Another thing to consider is that CD-check DRM does prevent some casual piracy. It doesn't prevent people who know how to use torrents and all that, but it *does* prevent people who want to just let their friend borrow the disk, install it, and play it without the disk. Not everyone is equally sophisticated, and even if DRM prevents only 10% of the stupider pirates, that's 10%.
That's actually a pretty good point, I didn't really think of that. Back then when I was a "casual pirate" (as was like everybody else) you really just had to copy the CD with a CD-Burner (if you had the luxury of owning one) and be done with it.