Ubisoft had success with UPlay in the past

The whole case is about Valve forcing other storefronts to sell at the same price as these publishers sell in Steam. Key point is that allegedly Valve requires this even if the game is sold not with a Steam key, but publishers own. Allegedly. Time will tell if they actually do it or not.

So far Ubisoft and WB hasnt had a great reputation in gaming community, so there should be no surprises why most gamers side with Valve.