It's also better in case your computer crashes or fries, you'd loose that game you paid $50 for! That what happened to my Warhammer: Mark of Chaos.
Normally if you explain and provide proof of purchase they will let you download again.. Or they damn well should. I have actually heard that the activation key for blood bowl can only be used 3 times ever. I find this disgusting, I get a new computer or have to reinstall windows/format close to every year, so people who legitimately spend their money and buy the game can only install it 3 times? I have had some pretty bad experiences buying PC games lately, GTA 4 was absolute hell to install. Took me about a week before I could actually play it getting past all the stupid security. I was screwing around and geting frustrated while people who illegally downloaded the game were happily playing away having cracked it?? Does not make sense at all to me, plus I hate that I had to sign up for windows live, I didn't want to make an account and I don't think I should have to install 3rd party programs on my computer that I don't even want just to play a single player, offline game. And even though I bought the game from a store, after it had finally accepted my registration it wanted me to download the thing from Steam again! What the hell was on the disc I paid money for then?? The excessive security is really killing the PC industry for me, and making me get dodgy copies rather than paying money (hell people are going to crack it no matter what security you use), they work sooo much easier and quicker. /Rant over.
It's true though, these companies are trying only to stop people from getting their game illegally, which is all fine and dandy until they start making us regular customers suffer because of it! Not to mention it's annoying because the people who download it illegally are still doing so!
Are you sure the security is not like Norton and you can install it on 3 computers? 3 installs seems dodgy.