Sure, there are some people who are invested in the cause, they're not social events only. But a large number of those showing up are not, they're there because their friends are, because it's an event and something to do, and because they want to belong to a tribe, and tribal outings are the thing to do when you want to be a part of the tribe.

Most of them don't want that more than they want to stay dry though, so bad weather usually translates into smaller events.