I always wondered about the world where you buy a licence directly from a developer or publisher, and then paid for a content service to download the game from, such as Steam.

I was also wondering if the licence could be some form of asymmetric key which could be used to "unlock" the game, but that might be a solution looking for a problem.

I don't think this would ever work in reality, because it limits the ability of the delivery service to double dip.