Nah, I see what you mean, however there are other ways. For example there are sperm banks.
But to the fact as well, there's no law that says we have to breed. I mean the human body is made for breeding, but what does it mean that we did not pass on our own genetics?
Especially, there are foster children and such that don't have proper homes (yet), and where adopting would be the preferable method. I mean, it would suck for a kid to be in an orphanage for 17 years of their life... There are even straight couples who cannot reproduce either, or those who chose not to have children. In that case, gay people aren't alone.
The funny thing is, one of the reasons why sex is so 'pleasurable' is because in a certain part of the brain, a warm good feeling is felt because essentially we are reproducing... Rewarding that behaviour. I believe it is also chocolate and a few other things that trigger that part of the brain as well.
Hope that clarified a bit.
EDIT: And lol porygon-z, while it hasn't happened to me, I know it might come to a bit of a surprise once I tell my coworkers and friends and such XD