In the case of iD's stuff, they are. Activision really only distributes the stuff for them.
In the case of Epic's stuff, the story is the same.
Not all games are licensed in a manner that allows for anything other than meatspace distribution. To point to UT and to presume that everything is like that is applying chop-logic for your argument. One doesn't lead to the other. It SHOULD, but it doesn't.