Because they're actually closeted gay people, OP.
Do you really not know why this started? This is nothing new. I "hear it all the time", too.
No, it's actually become fashionable - it's the straights COPYING the closet cases.
Actually, gay celebrities playing the pronoun game is a good thing, because this means they refuse to lie, which is far greater evil.
Yup, yup, r2 - gender neutrality never occurs
except in song lyrics - lots and lots of song lyrics
"Do you need anybody
I need somebody to love
Could it be anybody
I want somebody to love" (Beatles lyrics 1960s)
"When you love someone" (song title - Bryan Adams )
"To Love Somebody" (old Beegees song)
"Somebody to Love" (even older Jefferson Airplane Song) -
"Somebody to Love" - Queen
Not to mention lots of recent stuff by Enrique Iglesias, Justin Bieber, and so on
For whatever reason, it's been pretty standard since the 1990s for str8ths to use gender neutral pronouns.
English is a highly eclectic and mutable language and I don't see why "they" and "them" can't evolve into a gender neutral pronoun that can be both singular and plural, sort of like the German pronoun "Sie."
I think it owes as much to an odd sort of dumbed-down puffery of language in which "myself" is now widely used where "me" or "I" is correct.
See also, "gifted" and "price point", to name just two
The gays do it first, straights make fun of them, then the straights copy the gays.
It's just the way English works, not invented by gay or str8t
It may be more convenient or preferable for some to use gender-neutral for their own reasons
It's becoming common practice, b/c it's a way for people to remain vague if they choose to regarding their own preference. Additionally, it's a way for people to include others, demonstrate acceptance, avoid the issue of sexual preference completely, or just plain appear as being politically correct.
I've always said "person," etc. without thinking about it at all, knowing that I only officially date one sex. I've never thought anything of my peers, of any orientation, using certain pronouns, until I started looking at forums online and learned about "the pronoun game."
I had straight religious friends growing up, and both sexes would say "the right person," and so forth, and I can't even recall any of them saying "the man/woman I'll marry."
Could it be a regional or thing? Or a generational thing simply unto the evolution of English?