Using a credit card or an ID are both just using a physical item to 'verify' an age of someone who may or may not be that person. Getting a credit card has a minimum age, so the end goal of age 'verification' is met either way although the ID has way more personally identifiable information like skin color, actual birth date, gender, etc.

It isn't like scanning an ID verifies that the person scanning the ID is the person on the computer.