I purchased Diablo II. The DRM wouldn't let the game run without the CD-ROM in the drive, even though I did a full install so all the files were on my hard drive. The game was intentionally crippled, making it less convenient to play. (What if I had another CD-ROM in my drive? What if I wanted to listen to an audio CD?) I installed a no-CD crack.
A couple years later I reinstalled it. It wouldn't play; it kept failing because the DRM said the disc was not in the drive. It was. I had to crack my purchased copy to play it.