My linked bank account does not showing up as option to add money to my Apple Cash card

You can use your bank information as well. The transfer is made over the ACH network and is free. It usually requires 1 to 3 business days to complete.

Instant transfers are done through the debit card network and you’re charged 1.5%.

Transferring funds to Apple Cash requires a debit card that is associated with a checking or savings account.

Why a debit card and simply the bank routing and account info?