Coelocanth: I sometimes buy DRM-free digital copies of games I already own so I don't have to dig out any CDs/DVDs.
But I'm so lazy I install all my games and keep them installed so I don't have to dig around for discs and don't have to wait to install it when I want to play. I have a 1.5 TB drive that's got around 90 games installed on it. That's not all my games, but it's close* and I'm... heh, too lazy to dig out the ones that aren't installed on it yet.
*Actually, I have a ton of Indie games I've bought and not yet installed (although I've backed all of them up), so I'm not sure if 90 games is really 'close' to all I own.
90 games?! I would go nuts if I've more than 10 games installed at the same time and prefer around 3 to 5 at top, otherwise I can't choose what to play.
Anyway, only 5-10% of the games I've bought here I own somewhere else but a digital part is one of the reasons I stay here.