I'm sure that, for someone who is primarily a collector, buying Steam games doesn't make a lot of sense.

For someone whose goal is to play the games they buy, however, it makes a lot of sense to buy a Steam game on the cheap, even if they play it for only an hour.

Consider a game that costs $2.50 on Steam - this is not uncommon; I've even bought a pack of something like 6-7 indie games for $10. How long does one need to play a game like that before it's "worth it?" Going to the movies costs at least $11 these days for a two-hour flick (if it's even two hours). That's just to see the movie - not to have it and be able to revisit it later. A game that costs $2.50 is, by comparison, a deal, as long as I get at least an hour's worth of play time out of it. Getting an hour's worth of play time is not hard to do.

There are games on Steam that I've bought for prices in that range with the intention of only playing for about that long. Blueberry Garden is an example of that. It's weird, experimental - I'm not sure it really fascinates me like some other games. But it's kind of fun to tool around in. I think I've played about 40 minutes and could easily do another 20 or more. I've gotten my money's worth from it; it was worth the try.

And, when it comes down to it, if you're talking about people who hoard with no actual plan of playing the game at all...what's the real, substantive difference between a digital pack-rat and one who buys shelves and a bigger house to keep all their stuff in? You could argue that the digital pack-rat is being a bit more practical about their hoarding compulsions. Unless you go down the path of saying that collecting hard-copies of games has "resale value," which is in a lot of cases can be a somewhat dubious justification / differentiation, because there are a lot of hard-copy games (maybe even the majority of them) that will never be worth their original sticker price when re-sold.