[Smeaphvalialm]

I would suppose that a man with more testosterone is more interested in sex in general; and it requires a significant 'push' to overcome the societal pressure to be straight, thus only those with a strongish sex drive "come out" in any sense, even if perhaps some with weaker sex drives might, if society were wired differently, be gay.

Ultimately I would presume that the largest factors in gay/straight are environmental and not genetic; relationships in your childhood undoubtedly have a substantial effect on one's orientation, as does the culture you grow up in. There may well be some genetic basis, but environment surely plays a very substantial role.