I could never understand this myself. The only reason I could come up with was that those folks who did not take care of their things either did not work for them, did not appreciate them, or simply did not care.
I always treated my games well, and the cartridges still look as good as the day I purchased them. If I have any cartridges that are damaged, it is because I bought them that way used.
I still have fond memories of going to FuncoLand, and buying up all of their overstocked Sega Genesis titles, for about $2 each, which is how I amassed a lot of my collection.