Society rewards the institution not the individual.
Society rewards marriage because it maximizes the futur of society. Homosexuals are under teh mistaken notion that an individuals ability to enjoy an orgasm is involved.
Actually, it's not just the homosexuals. Most people since the '60s have viewed marriage as being about legalized or legitimized sex. That's why the free love crowd wanted to do without marriage. They didn't see why sex wasn't legitimate on its own.
Marriage is about uniting the man and woman into one flesh. Dogs can have sex. Dogs can make little dogs. But only people can marry.
Shalom.