What? There are many. And what's more, there are even quite a few packaged goods that actually increase in value over time without becoming functionally different (jewelry, paintings, etc.). There are any number of "investment" goods to which this applies.
And as others have mentioned, games do have a natural process of deterioration. The data itself may not age, but the technology certainly does. Technology, like "value" itself, is a relative measure that is subject to wide fluctuations in function and relevance.
The whole debate over used games is a distraction tactic from bloated publishers. The reason developers are hungry for the cash "lost" from used game sales is because the industry as a whole has become less stable. Publishers keep growing in size (more execs, administrators, producers, suits of all stripes), while developers bear all the financial risk. But blaming consumers for the industry's financial losses is misguided. The real problem is a busted publishing system.