Nah, think again, in either the merchant's or bank's perspective: how can they tell you are really who you claimed to be? That's the core question and why all the hustle. And again, even some design can perfectly solve that problem, there are additional problems to resolve: how to implement that change with reasonable cost, within reasonable time frame and with good user experience? And most importantly, does not break existing facilities. That's exactly how we get into the current situation, there are simply too much historical burden and while someone is trying to make things better, there maybe more organizations are putting sh*ts into it. For example, I really don't know if there were any banks ever used 5 digits PIN, but there are POS machines only accept 5 digits.