shmerl: That's why release shouldn't be tied to a distributor (i.e. shouldn't use any lock-in like Steamworks). Then testing and QA wouldn't depend on where you distribute - same version goes everywhere. Of course if developers shoot themselves in the foot and start using distributor specific stuff in every version - they'll have to spend more on maintaining those differences.
Elenarie: Still the same applies even if you don't use distributor-specific features.
There is also matter how much time and resources would have to be spend on developing and maintainaining features that distributor/client would essentially provide for "free".
