But programs (it's not just games, folks, it's all programs) are something very new indeed. If you give a book away then it's gone. If you give away a program, it's still sitting there on your computer unless you delete it. How does the company know if you did or not? You can make the program require a CD but then you would need to keep your Windows CD in the drive, your Office CD in the drive, a few game program CDs in your drive… it would get stupid very, very fast as you either have to get a full tower of CD drives or do a heck of a lot of swapping.
So what the software industry did was LICENSE the program to you - like leasing a car for a flat rate. You don't buy a program, you buy permission to run the program on your computer. That license is not something you can resell.
But people just don't understand that. There's an AutoCad case running through the courts right now that might shut down the used program industry but I think it's more likely that companies will just change the situation and start moving to thin client (marketers like to call it cloud based) setups. You don't get the program on your PC ever. All you do is log your computer in to the owning company's server and use the program on their computer. That actually matches what the licenses were supposed to be doing all the time - the company still owns the program, you are just paying for the right to run the program.