Who says we can't provide those interfaces to the container?

My view of it is less like containerization to provide complete isolation from the host/guest, but instead containerization to make the whole game a single 'entity'. Want to move the game from one system to another? Copy the container, that is where everything exists. No running around your filesystem looking for where the game decided to drop random files. Modded out the game and you break something? Just roll back the container.