a modest investment keeps people interested and builds a community of engaged users, which in turn gives you a usable board (e.g., this one)
it also serves as a barrier to the kind of people who exist only to take out their sad existence on others
the third reason is that there's absolutely no benefit to whomever sets up and moderates any free board on any subject other than a closer relationship with their cardiologist, and yet when you inject sports into the mix it somehow only gets worse for them