There would be far less regrets if the regretters had been aware of more options to express their gender-identities.
The fact that there were more regrets backwards in time then there are nowadays, is simply because more and more people nowadays are aware that they necessarily don't have to confirm to either a strict male or female-role only, just because they are not satisified with their birth-assigned gender.
Many of the people that have had Sex changes done and regetted it, have realised firstly afterwards that they were not really transsexual at all but something else, such as maybe Bigendered, Androgynuos or perhaps just intense crossdressers, but resorted to a sex change because they did not know how else to handle their feelings and believed a change was the only solution.
An Androgyne may actually suffer from body dysphoria aswell, although He/she may not want to actually have a conventional "change".
And ofcourse, not to forget, the claim that someone "can never be a real woman" if the individual don't have full surgery, is a rant that is unfortunately nothing unusual even within the T-groups.
Then, there are also those that don't actually seems to have regretted what they did but rather seems to have been brainwashed into "regretting" it, usually by religious conservatives, although these individuals originally actually claimed by their own words that the change was the right thing for them.
One such example is Alan Finch, that became Helen at the end of the 1980's and happily stated in an interview back then that she would "never regret it", only to some years later move in with a woman that "encouraged" Helen to de-transition into a man again, which she did, turning her moody and instable, getting more and more angry and wanted someone to pay for that anger, whitch turned out to be his surgeon, who Alan(Ex-Helen) now blamed for even operating on him, hence deciding to sue the poor surgeon. In fact, he decided to sue the whole clinic.
http://zagria.blogspot.com/2008/03/by-careful-what-you-wish-for-1.html