Apple requiring a payment method such as a credit or debit card is not an uncommon observation. Some possible reasons are outlined in the links below such as outstanding balance, an issue with a payment method you have currently entered, or ongoing subscriptions.
If you can't remove your last payment method or use no payment method with your Apple ID - Remove a payment method from your Apple ID - Apple Support
- If you have any active subscriptions, you must have at least one payment method on file other than Apple ID credit.
Also:
How App Store and iTunes Store purchases are billed - How apps, content, and subscriptions from Apple are billed - Apple Support
Some purchases aren’t charged to your Apple ID balance
- Some subscriptions might not be charged to your Apple ID balance.
So the resolution will be to add a functioning payment method:
This document explains how to 'Change, add, [review,] or remove Apple ID payment methods' on a Mac or Apple mobile devices; click here --> Add a payment method to your Apple ID - Apple Support