There is a loss of quality with games---the discs still get wear and tear. One of the reasons I'm wary of buying used games is that the disc is almost always badly scratched.
Perhaps a way that game developers can combat the sale of used games undercutting their current offerings is to make games that are so good that people don't want to part with them so quickly.
While I'm sure it could potentially be a problem in high-churn stores like gamestop, most places do have a replacement policy on discs that are scratched at purchase.