The reason behind the choice of having custom avatar and title only after a certain amount of posts is pretty obvious and simple: there are many people who just come and post a couple of times, then they disappear. All they want is custom avatars and people to make signatures for them. Then, once they got what they want, they don't come anymore. The purpose of a forum is posting, not having optional features enabled. For those who stay some time this becomes evident, and they finally can get, with no much effort, the avatar and the title. For the others, I'm sorry, but I don't think they need them, since they're not intentioned to stay from the beginning
It'd be much easier to have them enabled from the beginning, but no, I don't think it's fair
Hope this explanation was helpful to make you understand my point.