stores ask for pin in apple pay

For Apple Pay Cash? See the following from Manage your Apple Cash account - Apple Support

Apple Cash doesn't require a PIN as every payment is authenticated by Face ID, Touch ID, or a secure passcode. Some terminals may still request a PIN to complete a debit transaction. If prompted, enter a four-digit code such as 0000.

If using Apple Pay with your own credit or debit card, the pin is normally the card PIN you use to withdraw money or access your account services on an ATM.

Some stores may ask for this if the credit card or debit card is one that requires it normally or the transaction exceeds a certain amount.

How to use Apple Pay - Apple Support