Why does App Store ask for a payment method to download a free app?

I believe this is part of the App Store contract. You need to enter a credit card even if you only buy free apps. What I personally do is to prevent in apps purchases and only enable the possibility to buy them when I am sure I want it.

To do that on your iPhone go to:

Settings > Content & Privacy restrictions > iTunes & App Store Purchases > In-apps Purchases

The AppStore tells me to add my credit card every time I try to download a free app I tried to download tiktok and it kept asking for my password I unlock my phone with as I enter it,it says it’s incorrect so I enter my number doesn’t work.I add my Apple ID doesn’t work. It tells me to add my credit card/billing payment