What's the common thread between American McGee's Alice, Call of Duty and Quake 3? They were all powered by id Tech 3. Like Unreal Engine, id Tech was heavily licensed amongst third parties, used in a wide variety of console and PC games; however, it seems that id (and new parent company Bethesda) is no longer interested in pursuing the middleware market.
In an interview with Eurogamer, id's Todd Hollenshead said that Rage's id Tech 5 is a "competitive advantage and we want to keep within games we publish." Certainly, the awards the game picked up at E3 -- including "Special Commendation for Graphics" -- provide testament to that claim. From Bethesda's perspective, the engine is simply too good for anyone else to use. "We're not going to license it to external parties," Hollenshead explained. "If you're going to make a game with id Tech 5 then it needs to be published by Bethesda, which I think is a fair thing."
By restricting id Tech 5 to Bethesda games, id has essentially exited the middleware market, which is largely dominated by Epic's Unreal Engine. "Epic's made a good business out of that so kudos to them," Hollenshead said. "But I wouldn't change the way we've done things."