Personally I've only ever heard a few arguments whenever any Steam only game comes out and most of them are pretty silly.
1) I HATE DRM. Ok... fine. But do you own any of the following: any console, dvd or blu-ray player, a TV with HDMI, and practically every electronic device has some kind of DRM enabled. I don't disagree that less drm would be better, but to boycott something because of it seems a bit incongruous given the ubiquity of it in the marketplace. You'd pretty much have to crawl into a hole in the ground to totally avoid DRM products in general.
2) I HATE STEAM. Ok.. .fine. But why? Usually it's 'because it runs in the background', like your IM client, Skype, etc. so why single Steam out? You could always not have Steam running on startup and kill it when you finish playing if that's your cup of tea. Or it falls into the I HATE DRM, scheme so refer above.
3) What if Steam goes bankrupt. This seems like an odd argument. Look at the current high profile shutdowns of APB, Dirt, and all the old sports game servers. These seem like much more pressing concerns than Steam going bankrupt. Not that it isn't a 'possibility' of course.
The only actual legitimate concerns I've heard are
1) Bandwidth usage in areas were internet is metered or is at some ungodly slow speed. This is definitely unfortunate. It definitely underscores the digital divide that exists.
2) Inability to control patches locally. Though this is usually related to the above issue, where users want to control patch downloads either due to bandwidth problems. Civ5 had an interesting discussion where because specific patches are so gameplay changing that users didn't want the latest patches to totally screw up their existing saves. That problem seems to be pretty Civ5 specific though. The bandwidth problem is usually the most often cited issue with patch controls.
Admittedly I like Steam, because I live in a region where I can fully utilise the capabilities of it to my advantage. I realise that other people who are disadvantaged with bandwidth either by cost or availability would dislike Steam.
I think ultimately devs choose Steam due to it's advantages over competing download platforms. Most notably the availablity of achievements, automatic patch management, distribution cost reduction, and DRM.