The Europeans seem to manage to remember their PINs okay. And Americans seem to be able to remember the 4 digit PIN to get into their smart phones. And the PIN for their ATM cards. As long as the customer can set the PIN themselves, I don't see why Americans should not be able to remember a PIN for a credit card.
Of course, when people set their own PINs (such as their ATM PIN), they use something like their birthday, their child's birthday, etc. I don't see that as a real problem.
Mike
Go into the world and do well. But more importantly, go into the world and do good.