Nope, if I want a game, i'll buy it wherever's cheapest - Origin, U-Play, GOG or Steam doesn't really matter to me.
I understand your viewpoint, as a lot of the publisher specific clients are a load of tat. The only way this will ever change is if customers vote with their wallets - if sales suffer, i'm sure they'll release it on other clients.
Then again, why not give them a shot? U-Play and Origin have vastly improved (still no-where near as good as Steam, mind) in functionality and stability since their early days, and the only way the clients will get better is through community feedback. Steam was the same - many of the functions we take for granted were community led ideas.