I don't know that it should be illegal. I think the argument would be that it's deceptive. DoorDash, for some customers, claims there is no service fee - it's "free." What they're really saying is: the service of our delivery may be free, but the overall service we will provide is hidden or obfuscated in menu items, and without doing some research at the restaurant, you'll likely not notice.

One could argue it's best for the consumer to very clearly understand how much more they're paying. If not a service fee, here is our aggregate food markup, in plain sight. Transparency, in other words. Let's not borrow any ideas from the healthcare system.