Steam's actually a really good service. I have more than one computer, and I'm usually imaging one of them for some reason, or installing a new partition, or tinkering in some way or another... Steam allows me to just install the lightweight management program they have, and then painlessly download my games again... with updates. I've purchased a few single player games there at good prices, and it makes my life easier.
Of course, I could go to a torrent site, download the install, then try to find a legit cracked exe, then search for patches, and waste all kinds of time, or I could just buy games at a fair price off Steam and be done with it. My time's worth too much to be jacking with fucking torrent sites, and piracy.