There’s lots of varying reasons. To be honest, one reason is because straight, white kids don’t feel like they have a “say” in politics any more since they aren’t in a minority group... so they’re making minority groups to feel like their voice matters. Its honestly just more meaningful to admit you aren’t a minority but support them, but that doesn’t get you the recognition of being a minority, so pretending will have to do for some people... that isn’t everyone of course, some people are just questioning and caught up in all the confusing labels that have been creating to describe every micro-identity. Its also a sort of western individualism, we feel like we have to have some sort of key word to describe our whole personality and identity to anyone in a few words, instead of just explaining your preferences to people as you get to know them. Lots of “sexualities” are things that are really preferences, not a sexual orientation. For example not liking people you don’t know well aka “demisexual” isn’t its own sexual orientation, just a preference within someone’s sexual orientation. We’re just at a weird point (possibly because of the internet and social media encouraging us to summarize our whole selves in “bios”?) where we feel the need to have tiny individualized labels to describe our whole identities without talking in depth about ourselves.