A variety of reasons. There are those who are afraid of speaking out. There are those who fell for "You know how you guys were treated? That's how we're being treated now" and can't be bothered to even give it a cursory glance before believing it. Then there are the "I'm alright, Jack"s, gay people who are married or in longterm relationships who don't care what effect it has on younger gay people, they know they'll never have to prove they actually mean what they're saying and it makes them look good.