Why do I need a payment method to have something free

You need a valid payment method on file with Apple, even for free apps. They won't charge you for free apps but they need a payment method for ID purposes and in-app purchases.

Passedoff wrote:

I don’t want to put my card number on my phone. I recently was comprised using Apple Pay and was charged hundreds of dollars for nothing.

Putting aside the fact that Apple Pay is most likely not how your card got compromised, if the App Store is asking for a payment method and you don't want to use your credit card, try an iTunes/App Store gift card.

I agree, I don’t think that you should have to put your card number on your phone especially for FREE apps. Even when you could put your card on your phone anytime you want to that should be completely understandable, just not to have to put it on your phone.

I don’t want to put my card number on my phone. I recently was comprised using Apple Pay and was charged hundreds of dollars for nothing.