“So they get punished for having sex with a girl like they are encouraged to do but homosexual sex is rewarded.”
I don’t think that is the case.
Depending on the jurisdiction, people should only have sex with persons that are of age.
Aside from that, no one is going to be rewarded for being gay or straight, but will be responsible and either not having sex or not getting anyone pregnant.
Go to your local high school and see how many pregnant girls you see and then go to your local university and see how many pregnant students you see.
You will almost always see more at the local high school.
Cui bono?
It’s hard to justify having a robust police and court presence if there aren’t criminals. Solution: make more criminals. Teenagers fornicating? Make it a criminal offense and voila, more criminals!