When you buy a disk, who owns it? Is it you, the consumer, who paid the money, or is it the company whose software is on the disk? Do you have the rights to use of the software, in exchange for its purchase, or is it an area where the software you paid for is still the company's, therefore you paid good money for the disk and a limited usage?
When you buy a book, who owns it? You, the consumer, who paid the money, not the company who sold it. You have the rights to use it, without having it locked up, without reciting a code, without using it in only three places. The book you bought is yours to keep. This does not mean that you can copy it, but it means you can use it however you want, with no restrictions.
That is why I hate DRM with a vengeance. I buy a book, I get hours of enjoyment, and something I can keep. When I buy a disk, I find that I can only use the program in certain ways. I wanna be able to shape my game, tune it to myself. I'm not gonna steal a game, merely re-imagine it, like I do when I read a book. I don't have to follow TOS with a book, no EULA. I get the contents. I can't steal them and re-sell copies, but I can sell my copy to anyone, or use it freely. So, why is a disk different than a book?