I think you misunderstand the meaning of bloatware.. People use the features in Steam, they're useful, which isn't bloat.
And I presume by "smashing adverts in your face" you mean, opening a window with an advert or two, that can be instantly dismissed when closing a game for the first time in your logged in session.
What's that? you don't want any adverts? Untick the box in settings then? Want to start the client up in the library? Tick a box saying so.
Compare this to say.. Origin... Which doesn't "smash adverts in your face" at all. Apart from say when you start the client up, get directed to the store front page and get a pop-up window telling you whats popular today......
And lets not ignore system usage eh? That's important when deciding if a program is bloated or not. But wait! That can't be right, Origin is using more than six times as much memory as Steam after just launching and opening the client?
Steam is bloatware? You wouldn't know bloatware if it came and smashed it's huge Crysis promotion in your face.
Yes! Let the light of Steam shineth and revealeth that Origin is for hEAthen scum! May Steam be upon you all, Gaben-u Akbar!