Unfortunately marriage is part of the political institution, and receives certain, specific benefits under the law. As a result 'tis something that the government has a vested interest in controlling. I agree that what one, two, or more consenting adults do in the privacy of their own space is of no concern to the "powers-that-be." However when those adults decide that they want protections under the law, then they place themselves in a position where the government can, and must, dictate their actions. I may not like it, however that is how laws are structured.