I would argue that none of these are the case.

I have to disagree. People use PerlMonks for all those reasons, and many more.

People want to have a say in a node's reputation. And if there is no -- vote, then those who would like to see the reputation of a node depressed have no more influence than those who don't have an opinion either way. Indeed, no more influence that those who have never even read the node. That's not fair. That is why we have downvotes.