Honestly, why does it seem as though people don't like Steam? What's wrong with it? You purchase the game in one centralized place where you can download it an infinite amount of times and use your games in offline mode as well.
Plus, you get the insanely useful Steam Friends list. I just don't really see a point to not using Steam at all. It should be the one and only online distribution service.
People don't like it for all sorts of reasons - most of which are illegitimate.
It's the most popular digital delivery service so there is going to be natural hate for it by the underdogs, it makes it more difficult to pirate games, it requires a client to be running to play any games you bought, and apparently someone on here was complaining that steam auto-patches games which I thought was a clear selling point but I guess not.
People also don't like that Valve can ban an entire account if any illegal activity happens on it.
For the most part, and this is a generalization I'll probably get flamed for, a large portion of steam haters are people who have generally gotten away with exploiting the system by or because of piracy. Some other people just hate it because they think Steam is a part of an evil plan to invade your computer system and control what you think.