Exactly.
The institution of marriage evolved because of the need to protect children until they become self-sufficient. The legal framework surrounding marriage deals with inheritances, ensuring that those children are provided for in the event of the death of one or both parents, and that wealth stays in the family.
Sorry, homosexuals, marriage is not and never was about getting a certificate to officially sanction a sexual relationship. (Not that that consideration was behind the push towards "same-sex marriage"--one major motivation was to get what they perceive as financial benefits that married people have.)
Exactly. It has a necessary societal purpose which is not only not met by queer "marriage", it is actively undermined by such.