The main problem with rewarding developers is that the person who would be paying them does not get paid.
For example, I could make a budget for development on a server with my own money. It would be no problem to pay developers under the table for their work (other than that being illegal) other than the fact that I would be ultimately paying for Cyberjoueur's success and benefit and not my own.
Even to pay level designers or scripters something measly like 50 cents per level would be uneconomical. I still would consider doing it, and have considered it.