The user base here is getting older and the site needs more new users to keep the flames so to speak. If a new user stops in and can get their information in 1 post then they may be on their way shortly thereafter. If 10 posts over two days means there is some effort put into seeing other threads and sparks an interest in being a longterm user then it is doubly useful as a spam prevention and user collector mechanism.

That being said it is sometimes annoying to read the same thing over and over: "I am trying to attach photos and I can't" "you need 10 posts".