Fair enough, I did know about the offline mode but never used it. However it still doesn't change the fact that for any online play it requires you to be connected to Steam. My point (which obviously wasn't written) was the MAS doesn't require you to be connected to it for any online use of the games/software you bought, Steam does. If I'm still wrong feel free to correct me.
And Aspyer makes you use GameSpy most of the time. EA will eventually force us to use Origin (if they ever get it on Macs). There really isn't any issue there as Steam is:
1.) A Store
2.) Game Preference Cloud Storage (and limited image/file storage)
3.) Chat System (audio and text)
4.) Matchmaking service
Developer don't have to use Steam for matching making but many small developers who use the Source Engine as their base do.