Why do the majority of women still take their partner's last name?
Back in the medieval ages when a woman was married to a man, they were basically considered property for my understanding and treated like an extension of the man's person and family. So it was customary for women to take the man's last name since they were being joined to his family. But now here in the 21st century women are fully independent and last names don't really seem to mean much of anything. I mean what is Smith or McGregor or any last name really mean anymore? Especially in the digital age, lots of people have digital usernames like SarahSmith1727373. So the last name clearly doesn't mean much anymore.... Which leads me to wonder, why do the majority of women still take the man's last name? Especially when some of them have a horrible last name? I have seen some butt ass ugly last names recently, like Fink, Weimer, Slotsky/Slotsky, Hiscock (no joke this is a last name), Hardman.... And then you hear the woman's name and it's like something way more reasonable and less stupid sounding like Kingman, or Harrison, Walls, etc.
Pew Research has survey data germane to this question. As it stands, a clear majority (79%) of opposite-sex married women changed their family/last name to their husband's.
But for never-married women, only a third (33%) said they would change their name to their spouse's family name. 24% of never-married women were unsure whether they would or wouldn't change their name upon marriage.
From this data, I would conclude that while the trend of taking the husband's last name is fairly entrenched right now, the public's attitude are changing and we might expect the popularity of this to diminish over time. The detailed breakdown by demographic shows that the practice was less common (73%) in the 18-49 age group than in the 50+ age group (85%).
However, some caveats: the survey questions did not inquire into whether the never-married women intended on ever getting married; it simply asked "if you were to get married...". So if marriage as a form of cohabitation becomes less popular in the future, then the change-your-family-name trend could be in sharper decline than this data would suggest.
Alternatively, the data could reflect differences between married and never-married women. Perhaps never-married women -- by virtue of not being married yet -- answered "would not change name" because they did not yet know what their future spouse's name is. No option for "it depends on his name" was offered by the survey. Never-married women may also more-strongly consider the paperwork burden -- USA specific -- for changing one's name.
So does this help answer your question? Eh, only somewhat. Younger age and left-leaning seem to be factors, but that's a far cry from cause-and-effect. Given how gradual the trend is changing, it's more likely that the practice is mostly cultural. If so, then the answer to "why is cultural practice XYZ a thing?" is always "because it is".
Thanks for providing this really detailed and interesting reply. Lots of good insight here. For the 'Postgraduate degree' group, I wonder if they're dramatically higher due to the frustrating problems associated with name changes? Like if you publish an academic paper with your full name, you can't easily go back and change it, so that may affect it... huh.
I have friends who published before being married, so now professionally still use their own last name (for continuity) but socially will go by their husband’s last name.