Sexual Reassignment Surgery isn't a symptom of society viewing being trans as a disorder. Srsly. A lot of transgirls (and transmen, even though they're pretty fucked when it comes to getting a penis*) really can't stand their given genitalia, and it's not because they're trying to conform to some constrictive gender role. And there's lots of transwomen who really aren't too emphatic about getting a fancy new vagina, but would like to anyways, just because it's more fulfilling than having an annoying reminder of your chromosomes swinging in between your legs. There's even some trans people trying to make it seem more "normal" by just saying that being trans is a birth defect, and nothing more, so it and attempts to transition should be treated like any other birth defect and attempts to correct it. (But I'm all for delivering a big "fuck you" to the "let's all try to be really normal" community.)
*phalloplasty, the surgery that gives transmen dicks, is still a not so great alternative to having a vagina, which is why there's more non op FtMs than MtFs. While vaginoplasty can create very natural looking genitalia, phalloplasty tends towards some really weird looking pen0rz.
Fake edit: RBG's post reminded me that I completely forgot about top surgery, but then I remembered that essentially the same argument applies, except transwomen grow them naturally with hormones and transmen need a mastectomy.