Gamers can be resistant to change. They know one gaming system, and they may not want to have to learn the rules for a new one. That can be tough if you don't want to keep playing in the same setting all the time. Thankfully, there's those out there that are changing up the locations of games but still using the rules you know. Take Genefunk 2090. It's a biopunk/cyberpunk setting using the OGL rules system. It's also up on Kickstarter now.