Theres two points that I see here:
1) Convenience/ease of purchase
2) Low enough price to accommodate impulse shopping
The Steam deals definitely do this and I've often bought games on Steam for exactly those reasons. Theres a lot of games which I would never have thought about buying, but then I see them there for €5 and all I need to do is click and wait for the download and it looks fun... why not!? So yeah, if somethings convenient and inexpensive enough to buy on impulse, people will.
My primary experience with Steam was Bioshock, where I was forced to pay quite a bit more than the local reseller rate in order to get the game - local reseller was sold out, and only had Xbox versions left. That, and other Steam annoyances, mean I'll likely never buy another game from Steam.
But you're certainly right about the convenience factor. Considering Apple app store: the fact that I don't have to dig out my credit card, and don't have to wait for a big download or - even worse - a physical delivery, and don't have to fiddle with installation, makes all the difference with installing app store applications. Pity the business proposition for the platform is so crap, though (fascist Apple), or I'd try my hand at developing for it.
I picked up Bioshock on Steam when it was on sale at $5 -- which was fortunate because that's approximately what the game turned out to be worth to me: the thing would rarely run for 30 minutes before crashing. A long thread on the Steam message boards revealed that others had similar problems, with no known fixes.
I suspect that the game's publisher (2K) saw Steam as an easy alternate revenue source that didn't need stringent testing or support. I have purchased a number of other games on Steam, and I have not had an experience nearly as bad as Bioshock. The Valve games, in particular, are wonderful -- fast-launching, working on a range of hardware, and constantly updated to enhance the player experience. I'll think twice before buying another 2K game for the PC, however.
Anything you buy on Steam is effectively a rental, though, so it's important to pick a rental price. Their terms of service make no provision for the case where they go offline or out-of-business, and you can't sell or transfer the games to someone else. $5 was not a bad price for "renting" Bioshock, frustrations aside.
Oh I agree. I don't really like Steam and (usually) refuse to buy anything that hasn't bee greatly reduced. Normally, I'm very reluctant to spend more than €5 on Steam.
But.. when the price is right (less than €10 in this case) and something looks good, its damned convenient and I'll simply impulse buy.
The Steam deals definitely do this and I've often bought games on Steam for exactly those reasons. Theres a lot of games which I would never have thought about buying, but then I see them there for €5 and all I need to do is click and wait for the download and it looks fun... why not!? So yeah, if somethings convenient and inexpensive enough to buy on impulse, people will.