Consumer protection works both ways though.
Another function of Apple's rules is to protect the consumer from bad behavior by apps that lead the customer off-app to other payment flows for abusive services not under Apple's review.
If a company wants to do this, and the consumer wants to fall for it, that's between the company and the consumer. But if they promote it and lead the customer to it using wording and other elements situated on Apple's curated app platform, Apple becomes responsible for having allowed it, and it both hurts the consumer, so they are not protected, and taints the experience on the Apple device.
This built in consumer protection is part of why Apple has a reputation as having good user experience. By keeping the rules in place, Apple helps maintain the valuable reputation it has earned for having good user experience which includes, as a vital part, this consumer protection.