Revned's right. Us regular posters/mappers already all have our own pet projects that's occupying most of our free time and there's just no incentive to drop everything to fulfill the seemingly endless list of requests. Especially when the people asking have no idea how much work is entailed by even the simplest mapping project (NES, GB, etc), much less for a modern PC or console game.
Heck, I've got projects at various stages of completion for which there are requests, some of which have been lingering for years. Guess what? I'm not going to suddenly rush back to them just because someone asks for them again. That's not how I work. I know it might sound stupid, but mapping to me is a creative endeavour. If I'm not in the mood or don't have the mental energy for it, nothing will get done. No matter how often you might ask, no matter if you were even to pay me for it.