Attention whores.
And they do get the attention ... so it works.
That's really what is driving this. It has become "fashionable" to be "gender-confused" and attention starved people now have a path to get themselves noticed.
A boy can put on a dress and become homecoming queen of his high school. And he will almost definitely win because the other students will trip over themselves to vote for him, lest they be accused of being "homophobic" and insensitive.
Oddly, women trying to become men don't get the same attention as boys becoming girls. I think it's because society in general is hostile towards traditional masculine behavior and so they encourage men to emasculate and feminize themselves.