I think what you really mean is, “why is an OUT gay actor so rarely allowed to play anything at all?” Which is answered by another question:”Why do so many queer actors, particularly bi actors — and, Lord, there must be many — remain closeted?”

I was having a conversation with a newly out Hollywood technician yesterday, who pointed out that, of late, Matt Bomer seems to get all the parts written for an out, cis, masculine-presenting gay man. Doubtful that Bomer will ever come within a country mile of an Oscar… which has much more to do with his limited acting range than any skittishness industry peers might have about queer actors.