Theoretically it's fine. But as soon as we start catering to one sub-culture in these shows, every other one under the sun will want representing under the banner of them being discriminated against by not having the air time other sub-cultures have.
So that may be why it isn't already prevalent, because it's simply too much hassle.
Besides, i think there are other ways in which the concept of homosexuality, bisexuality and transvestitism and transexuality(?) can be taught to the young generations more effectively and safely.