Sadly, for most public figures coming out is an extremely risky career move, which in the vast majority of cases doesn't pay off.
If you're a hunky movie actor, you want to project a clean hut heterosexual image for your target audience and the sponsors.
Same for singers, athletes, etc.
It's a very sad state of affairs. Because even in places which are very tolerant, it's the same issue, as it's more the result of business/marketing and less of prejudice.