Everyone has ideas, but far from everyone can make games. The result is that we ALWAYS have a LOT of ideas on these forums, but far less people who can make use of them. I am working on a game of my own, and I have ideas for at least 5 other stories I would like to try out, and that's just me alone. Sure, little Johnny over there might be giving out 10 or 20 ideas for game plots, but why would I choose those, when I have my own ideas and creations?
Are there people with the skills to make games, but lacking the right idea? Of course, but these are the exception, not the rule. Even when those people post on this forum, mostly they are asking about specific fetishes, rather than an actual story idea. I simply don't think that there is a need for a "game ideas" thread, but that's just me.