Making a platform that was simply a copy of all of Steam’s features would certainly take a lot of time. That’s why to break into the space a new platform would need to actually innovate a killer feature that brings early adopters to it even without having all the bells and whistles Steam has. Then the user base can and will grow as you fill in the gaps so the ‘sacrifice’ of using your platform is lessened.

All exclusive games do is build resentment in your customers at being forced to use an inferior product.