I'm wondering about what cleanliness you are talking about, after all Steam (thankfully) never got a 100% market share (Games For Windows Live, Stardock's Impulse, GamersGate, Matrix/Slitherine, Blizzard games, Good Old Games, Ubisoft's horrible launchers, various boxes-only games, indies...) - if anything it has killed indie gaming that was briefly freed from having to have a full blown publisher and physical distributor - these days smaller developers have a hard time to sell from their own website and sometimes even to just forego from using Steamworks-only services (which make non-Steam versions second class citizens) like multiplayer matchmaking and mod Workshop.
(And some other programs like Xfire have tried to centralize game libraries too, also offering other services like chat, matchmaking, game hour counts, video recording and upload...)