If gays truly believe in equality, why aren't they fighting to get the government out of marriage altogether?

Gays claim that to not have the government recognize gay marriage discriminates against gays. But, they don't seem to realize that to have the government recognize ANY marriage at all discriminates against single people because it gives married people benefits that single people don't have. What makes discrimination based on marital status any less wrong than discrimination based on ual orientation? Gays make the argument that denial of gay marriage is a violation of the Equal Protection Clause because the government has no compelling reason to treat gays and straights differently under the law. Well, guess what? The government doesn't have a compelling reason to treat married and single people differently under the law EITHER. It doesn't inflict any harm or danger on anyone else to give single and married people equal privileges. Then there's the argument that ity isn't a choice and that gays should not be penalized for something they can't help. Well, being single isn't always a choice either. Some people never get married for reasons that are beyond their control, like never meeting the right person for example. I don't think it's fair that single people should have to pay higher taxes just because they weren't lucky enough to find a spouse. Do gays truly believe in equality for ALL people, or do they only believe in equality for gays and straights?