iTunes card
keeps asking me about payment I always used iTunes cards don’t want to put credit cards in
iPad Pro, 10
What happened before it started to require a payment method?
In general the store will not require one, unless for some reason its unable to charge you for something you try to buy, or if you had a Payment method and it stopped being verifiable for any reason.
In such cases, you will need to add a verifiable payment method to complete the request, and once that is done you can remove it if you do not want to keep it.
Note that for verification, Apple may place an authorization hold on it. This hold is reversed shortly after verification is completed.
See here: About payment card authorization holds from the App Store or iTunes Store - Apple Support