It's not. Would you install a random "Document Scanner" or a "Flashlight" app from the app store and be confident that it's not a scam that will sell you a overpriced subscription for little actual functionality, just because Apple has reviewed the app?
First, you would have to define what a scam is. Am I not allowed to sell a flashlight app with a $100/year subscription just because? Are you saying Apple should have the power to dictate to developers what they are or are not allowed to charge, and based on what yardsticks exactly?
Second, users do have tools to monitor and manage their subscriptions within the app, so it’s not like Apple is totally blind to the matter.