"arbitrarily using my father's for x number of years makes it mine but actively choosing another human being's does not? Interesting".
People don't just choose 'another human beings' do they, as if there is a smorgasbord of names to choose from and oh! they just happen to stumble across the same one as the husband. They passively take the husband's name - or rather, the husband's father's name if we're going down that silly route 
Agree with Saki - the reasons are often very silly or illogical, dressed up as if it was the only choice, or the most logical thing in the world.
"Having the same name as the kids" - well if he takes your name the same objective is achieved.
"I wanted us to be a family unit" - names alone do not dictate this, and anyway any old name will do this, whether it's the woman's, the man's, or one plucked out of thin air.
"Didn't like my name (for whatever reason)" - Odd that it's mainly women who ever seem to have such a laissez faire attitude to their own name. Wouldn't have anything to do with a culture which teaches society that women's names are disposable now would it?
"Family would disapprove" - let them!
Yet funny, apparently millions of women agonise over this decision yet all come to the same conclusion - the man's name. How strange.