Probably because of intellectual property reasons. If someone suggests an idea it requires a lot of legal wrangling to get the rights to produce it. Once you st

Probably because of intellectual property reasons. If someone suggests an idea it requires a lot of legal wrangling to get the rights to produce it. Once you start going down that road, then you have to justify budgets, ROI, compensation, etc. Additionally, if any game is made that even remotely resembles any part of the proposal, that opens up the potential for a lawsuit. It's basically the same reason that authors won't read your unpublished book and screenwriters won't read your unpublished screenplay.