And within 5-10 years, no one is buying it to play...

It's a moot point.

If the original buyer bought to play, they wouldn't wait so long the cart goes bad.

And after 5-10 years there's no reason to overpay for a sealed copy to play.

You can just pirate a dump of the game and flash it on if you want to actually play it.

It’s a cognitive dissonance thing for collectors. They want the preserved, playable copy but they don’t ever want to break the seal because that lowers the value.

I bet there are a bunch of collectors out there in possession of empty game boxes (with placebo weights) that have been expertly resealed and then submitted to grading companies for a seal of approval.