Hmmm. Interesting question, Mo. Being single myself, right now... and not planning in any regard to have more children, the only persuasive reasons I can think of right now to marry are more along the lines of a business arrangement... it's financially beneficial for both parties to have one home, shared insurance, and inheritance rights. Though in every instance, there are ways around those issues.
Emotionally, I see no benefit whatsoever in being married, as opposed to being in a LTR by choice. Actually, I see marriage, in many senses, as a detriment, if you are not with someone who is 'relationship' aware, as many people on this board are.
Were I to find that person, I would consider marriage again. But it wouldn't be for reasons of validation, or to keep from living or being alone in old age, or even for the business reasons I've listed.