I think the reason is multifold:
1) The Internet Wedding Planning Process-
So many brides today start their wedding planning online. They browse Pinterest, The Knot, wedding blogs, and all over the internet to gather ideas and decide on a vision for their wedding and beyond. Most of the initial thought goes into the wedding celebration itself, and the conversation/discussion of whether the bride will change her last name to his, hyphenate or keep her own name may not even come up until it's already been assumed that she's 'Going from Miss to Mrs'. The web is full of images of Mr. & Mrs.- pillows, coffee mugs, shirts, hats, luggage tags, champagne glasses, signs for the wedding, home decor, even engraved forks for the wedding! When it comes time for engagement photos, you can find thousands of couples online who have opted to go with the cute and clever
Him: I stole her heart...
Her: ...So I'm stealing his last name!
signs for a couple of playful shots.
Fast forward the planning a few months- the American bridal shower today is often full of clever, creative Mr. & Mrs. _____ goodies, from the invitations to the decor to the gifts that the bride receives, such as the mega-popular, personalized dress hangers (often found on Etsy) that say Mrs. ____. She wouldn't want to disassociate from this amazing, loved new persona, especially when she is getting so many things with her name on them, and they're helping make the transition into her married life so wonderfully real. Name change options may not be a discussion the bride thinks she needs to have, because she's already so looking forward to being Mrs. _____ and because...
2) Most people in our generation are doing it this way, so we are, too-
Okay, okay, if our friends all jumped off a bridge, would we do it, too? Umm..we might! This is much more harmless than that anyway, and represents something happy and fairytale-like in our own lives, so why would we want to go against the grain? This is known, it's common, it's 'normal', it's fairly easy to do (or we assume it must be, if so many women do it!), and it fits the getting-married mold that we are so happy to be a part of..
3) We may not realize that there are other options-
Honestly, when I got married in 2012, I hadn't even thought of changing my name a different way. If I had, the thought process would have gone something like this: Leaving it the same was too anticlimactic for me for such a big life change, plus I wouldn't know if I'd become Mrs. GivenName (that's my mom) or stay MissGivenName (that's who I already was), and Ms. had a different connotation to me. When I think of Ms., I think of a woman who is either divorced, widowed, or has feminist views and wants to be seen as a woman, but not specifically as a married or unmarried woman. I was excited to be a married woman, and happy to become a Mrs. That, to me, meant taking his last name. Maybe this view is misled or ignorant, but I imagine that if I was thinking it, then I'm not the only one.
Professionally, I hadn't made a big name for myself, and could easily and happily change my last name identity (and in fact, would probably be expected to) after the wedding. I've always liked my middle name, so I wouldn't want to drop it and move my maiden name into its spot. Plus, it's not a middle-name-type-of-last name, so I don't think it would look/sound right, if that makes sense.
The final option was a hyphenated last name combination, and I have mixed emotions on this. My oldest sister had a hyphenated last name growing up, and went through life up until her wedding with a very long name. She had her first name, her middle name, and essentially 2 (connected) last names. It had its moments of frustration, but it was her last name and it worked for many years. I imagine there's some relief now when she signs her much-shorter last name, but it will always be her maiden name (and it's so cool that she had the connection with half of our cousins that I did not, as I had only one of the last names). There are positives and detractants to any complicated last name- the spelling, spacing, pronunciation, length, any apostrophes or symbols/accents of any kind, including hyphens. I know that the daily tasks that involve writing, signing, filling in and explaining your name can be made more frustrating and time-consuming with a more complicated last name, and while I know it's right for some people, it wasn't right for me.
Of course, this is what I would've thought if I'd gone through the steps and known all the options, but I really didn't think about it at the time. I just jumped into the land and life of Mrs. Miller, and was happy to do it.
3) We feel that one last name is an easier way to go (if you'll be changing from your given name)-
This one's pretty simple. Literally. It seems that changing from one last name to another is a much easier change than any other option. I had 2 professors in college who were married to each other, and when they got married, decided to hyphenate their last names and legally BOTH of them changed their last names together. I think that's really special, it sounded nice and it was just right for them, but I know that it's a little bit more work to do it this way. In this case, the man also needs to legally change his name, so it costs more money, takes more time and is a bit more of a hassle. However, if it's right for you, it's worth it- and you'll have a buddy who you can spend time with during your wait at the DMV and the Social Security office!
When only the bride hyphenates her last name (more common in the hyphenating world), and then the couple has children, the children can either get a hyphenated last name as well or one of the two last names on its own. I feel as though these options could get a little bit confusing to everyone, including outsiders (teachers, coaches, friends, school personnel, etc.) and the children themselves, and therefore could end up getting frustrating. One last name for the whole family seems more straightforward, obvious and unified to me. It's easier, but not always the right choice for every couple and every situation.
4) We like the groom's last name, or didn't like our old one so much, and are relieved to change it-
My maiden name is Levenson, which I respected but didn't feel as though I had to keep in my name to keep in my heart. My new last name would be Miller, which was SO much easier in a million ways. I was excited to have a shorter, simpler, no-questions-asked last name, and did what I had to do to make the change quickly after the wedding. Mine was a pretty obvious change-it decision to me, and some girls experience that, while others go the opposite way, changing from something simple to something a little bit more complicated. However...
5) They love the person they're marrying and want to honor him and his family in a big way-
Again, getting married is a huge deal. When you've found your soulmate and someone you feel you can live with, live for and love forever, you take the whole package. Sometimes it means marrying into a name that you don't love as much as the one you previously had, but you do it anyway. In a way, it's how you show his family that you're proud to join their ranks, and how you show him that you belong to each other. Sure, some people could read into this choice as a symbol that you're showing you belong to him, and that could lead us into a whole other slippery debate about misogyny, #yeseverywoman and the general cultural images that are dangerous and retrograding for the women's rights we've fought for for so long, but it's not about that. We could also get into a discussion about how guys want girls to change last names for them to prove their love, but I think that many girls want to change their names in a situation where love is present and respect is part of the equation just as much. Sure, there are situations that happen where it's skewed and intentions are wrong, but I don't think that's why most young women have decided to change their last names to their grooms'.
No matter what, this is about love. This is about respect, honor and union, and when the time comes to make a choice, many young women are happy to become Mrs. _____. It's partially because we've been programmed and taught to want it, partially because we don't know or prefer the other options. We may want to take the easy road for ourselves and our future children, the pleasant route, and show a sign of devotion and dedication that we've never shown before and take the steps to change only our last names, as I did and many of my friends have done...or we may look at the options and pick something else that's right for us. Either way, it's good just to know what we can do, and go from there.