Apple does not store your credit card data. They generate some sort of tokenised account information with your card issuer when you first add your credit card. They do not store the tokenised account information, it is only ever stored within the secure area of the SoC on the device.

From that point, Apple is completely out of the payment equation. The tokenised data is used to generate a once-off payment authorisation with your bank when you pay for a product using Apple Pay.

But I agree with the point of your post: if Apple thought collecting data would result in a significantly better product, they would probably do it.