I'm more amazed at currency being accepted at all, the North Korean "Super $100" I hear is nearly perfect but slot machine bill validators still rejected it. I

I'm more amazed at currency being accepted at all, the North Korean "Super $100" I hear is nearly perfect but slot machine bill validators still rejected it. It's one thing to have custom made chips with RFID, notches, decals and who knows what else but to accept paper as a valuable item seems to risky yet most counterfeit bills are rejected all the time.