However, you must remember that the average "straight" guy pretends to be homophobic and thus does not want to see a guy who has either just had a dick in his ass or his dick in some other guy's ass going ahead and fucking a girl.
Sure it's stupid.
I'd much rather watch a bunch of "gay" guys fucking women and a bunch of "straight" guys fucking men simply because it's different, and in the hands of a good director, could lead to some very interesting psychological analysis.
But anyway, more often than not, when a "straight" star fucks men, his career is over. Sad but true.
The only real exception is Ricky Sinz who, despite being reasonably straight and fucking women in his private life, has become one of the most recognizable faces in recent gay porn (Raging Stallion) but has just purchased and is now shooting for/starring in content for Hole and a Heartbeat (his straight alma mater).
Ricky is the only recent actor I know who has successfully bounced back from straight to gay and then back to doing both at the same time.
[Link]