Don't they have to deal with those forgotten PIN calls anyway? Don't you need a PIN to get cash out of an ATM?

My debit card and its PIN are used for a few different things - in-store payments, using the ATM, and authenticating when in-person at a bank. The last one is interesting - each desk at the bank, both the tellers and the offices where you talk to someone, has a terminal and every interaction starts with putting in your debit card and entering your PIN.

Extending this to credit card is no big deal - my main bank syncs the PIN between the debit and credit cards. I only have a credit card with the other bank that I use and I haven't set foot in one of their branches in 20 years, so I have no idea whether they sync the PINs or use their cards for in-person authentication.