I think that the restrictions do make sense to a significant extent. I've visited some other forums in the past where there would be frequent spam posts because there wasn't enough restrictions to at least attempt to ensure that the accounts would be actual people, rather than say some form filling and ad posting robot.  I also particularly don't like doing things like going to forums and reading comments, and finding a bunch of those blatant automated ad posts.  So I think it makes sense to ensure better forum quality.