No Credit card on account

You have to have a payment method registered to the account to initially gain access to the App Store. After you have verified a payment method, you can remove it and have nothing registered against your account.

The payment method requirement is a security precaution that helps to minimise the amount of bots that have access to the App Store. It is also used as a form of identity verification, as, even if you download free apps, you are technically purchasing them for $0 and so registering that purchase against your name.

Change or remove your Apple ID payment information

Apple ID without a credit card  

Apple ID - If you can‘t choose None when you edit your Apple ID payment information