I'm with jcalder here, I also don't get it. I mean, I get the whole concept of grading, I know what it IS, but I don't know why people do it.
I'm the type to think that games are meant to be played, grading them and putting them in these plastic cases you can't open seems like such a waste to me. Heck, I don't even get why people collect factory-sealed games at all, graded or not, it seems so pointless.
If I ever get rich, my hobby will be to buy literal truckloads of super rare sealed retro games (and graded games), make youtube videos for each and every one of them where I open and play them, and then resell the games for a fraction of the price... just for the lulz