I think there are a few people who really do identify with a gender other than their biological one. But that is a minority, and lots of others are just going along for the ride for the fun of it. It’s kind of like that some small subset of people are truly gluten-intolerant (celiac disease) but lots of others jumped on the bandwagon because it is fashionable.
I am an extremely liberal person, but I really had to laugh at the choices on the CalTech application under gender: heterosexual, straight, lesbian, gay, bisexual, pansexual, queer, asexual, cisgender, intersex, transgender, transsexual, non-gender binary, gender fluid, or unsure/questioning. Wow! How’s a high-school student supposed to choose from that list?