Sometimes we overlook the smaller things, details that are just out of place because you don't want to ruin a delicate balance called friendship. There are things you don't mention because you don't want to lose someone.
None of them ever mentioned the fact that Kenny hardly ever had a lunch or any school supplies.
None of them ever mentioned the picture of two fourth-grade kids that Stan kept in his locker.
None of them ever mentioned Cartman's reluctance to mention his mother or where he got his money.
One day, somebody would and then their fragile universe would tumble down, breaking away to reveal the harsh reality- that they lived in a very cruel world that hadn't been kind to any of them. And then they would fall down, down, down, farther and farther into Kenny's poverty, Stan's history, Cartman's family. But once they'd fallen, none of them would ever be able to get back up on their own.
And they never would.
So for now, they just smile and turn a blind eye, hoping nobody will ever notice and yet already knowing that they have.