Why do i have to pay for a free app?

You don't have to pay for a free app.

Requiring a verified payment method does not mean you need to pay.

Once the payment method has been verified correctly, it can be removed as long as there are no active subscriptions or pending charges.

Once remover, it should not ask for a payment method again.

You usually need a payment method -

Unless you have a NONE option in the payment methods listed in your account details, you usually need to have added a valid payment method to your account. Even to re-download or update apps and for free apps.

The payment method must function properly for you to be allowed to use your account, regardless if you are updating a free app.

M1 Mac mini, macOS 13; Watch, series 7 GPS/cellular, watchOS 9.1; iPad Pro 2nd Gen, iPadOS 16.1; iPhone 12 Pro, iOS 16.1; TV 4th Gen, tvOS 16.1; HomePods, audioOS 16.1 and Airport Express w/ Airplay 2

Declined just means it was not accepted, not that it tried to charge you for something.

It is not trying to charge your card for anything. It may be trying to place an authorization hold on it to verify it can be charged, but these authorization holds are reversed shortly after verification completes.

It is not trying to charge you at all for anything. It just required the payment method be verified.