None at all. Perhaps it is to show oneself as an active member and not someone who just stopped in to drop a link. 19 posts in a short time frame is certainly strange.
There are settings on my other forum for post count minimums to access certain forums and there was also a rule about unnecessary posts to get to that minimum (it was called post count farming). A contribution could also get you qualified for access for a year in lieu of a minimum post count for many of those forums.