Connvienience comes first for many consumers, and it doesn't get much easier than Steam. And I guess no publishers saw a profit in selling ArmA 3 in North America.
I do understand them as DayZ will become/are Standalone and besides that it's a niche market - It doesn't appeal to the masses.
Convenience comes first for me too, and to me that means installing the game as fast as my DVD drive can read the media--not waiting the whole day to download a multi-GB game. And then do it all over again if I decide to move the game to another computer.