I'm just guessing but....
There's this weird phenomena where people have excess of something that's relatively rare elsewhere that they just treat it as... meh. Well... maybe meh isn't quite the right way to put it.
Let's say that you manage to gather together twenty-five examples of Game X from say some part of a estate lot, you're more apt to leave them on your couch or coffee table than someone who scrounges for ten years just to get one example of Game X. He probably didn't really have them in his car for a good reason (ie, taking them somewhere to be sold?) he was probably just dragging his collection to his buddies house or some party to show off just how big of a dork he really could be.
He was also probably relatively younger. Yeah, he may have spent ten years collecting them but he sure as hell didn't act like it. I used to trade/loan/borrow console games when I was much younger. All in all, I've had about half a dozen games stolen/destroyed/"lost" from me (not counting the ---smurfette--- of an ex that stole nearly half my collection). When you're younger, you tend to treat things differently than if you're older. Nowadays, I rarely display a large part of my collection and I most certainly don't let the vast majority of the people in the Real World™ even know I play games. Given the stories of PCB's stolen right out of the trailers/truck beds, I don't even let the truck out of my sight any more when I'm transporting.
No matter how I mull this over, I can't stop thinking what the ---fudgesicle--- he was doing carrying around forty (shouldn't it have been 50 if he was missing four titles?) PC10 carts in his car?