That last part is what I see as significant; I don't care that much when I got married, as I'm pretty sure I am now married.
My objection to the "why not do X" argument is that it doesn't answer the more pressing question: Why do X?
Why should people have a big formal ceremony? There are some reasons for which people like to do so. I don't think, however, that all, or even very many, of them are
good reasons.
When we did our legal dance, we invited pretty much immediate family and a couple of friends only. There were twelve people, total, in the room, and that's including the guy with the ability to sign the paperwork, all the immediate family, and even us. Or maybe eleven; I don't remember for sure.
In general, I think it's often beneficial to have marriage ceremonies, but I think it is very damaging to demand them, or to treat them as normative. Once we cross the line from "typical" to "obligatory", we are imposing new rules on people -- but, as Jesus put it, "from the beginning it was not so."
I dislike the elaborate legalism that seems to crop up about these things; people come up with additional rules, and the main function they seem to have is to get brought up as a way out of a marriage that's turning out to require some kind of work, or to be used so that someone can feel smug about being "really" married and look down on all them sinners out there who are just doing what Adam and Eve did. Only without the apple.
