The thought was to encourage people to join the forums so they could get points. There use to be a notification when you joined which explained that to new players but I think it got lost one of the times I updated the shop.
Me and Rigel had an idea to incorporate the shop into the forums, which required me to store all the shop information (items and points) on the forums database. Maybe not required, but it was easier that way. Since the information is stored in the users table I needed to have an account to store it under which meant it was necessary for a user to create an account before the information could be saved.