Mostly it allows everyone to keep up with the threads.
ANd it helps to eliminate posts that do not really contribute anything valuable to the forum.
There was a time in the early days, that some people came on and posted lots of posts in a big hurry to try and up their forum ranking--posts like Ya Right,
and Ajax rules. stuff that didn't actually say anything, or tell anyone's viewpoint about what ever the subject was. So the moderators decided to limit postings esp. after the forum got overrun with gamers, who didn't care about the movie.
WC and the mods prefer that posters post what they think and why, so that everyone takes their time, and actually contributes to the value of discussions while they up their rankings. hope this helps