App Store asks credit card

If you want to download free apps you may be able to select None for a payment method > Mac App Store: Changing your account information

If None is not available, read here > Why can’t I select None when I edit my payment information?

For paid apps > iTunes Store: Mac App Store: Accepted forms of payment

Hello! I think one of the options within the Mac AppStore is that you can select "None" for your payment method. This is just so to allow you to download apps that require a balance in order for you to download them, but if you select "None", then you will still be able to download apps, although these will only be limited to the free ones. I hope this helps!