But we don't have any laws or expectation that a food vendor is going to be acting in my best interests. If I want to spend my rent money on 87 large pepperoni pizzas, nobody is going to arrest the guy who took my order because he didn't sit down and have a 30 minute session with me to ensure that my order was in my best interests, fit within my budget, and would improve my life. All we do is make sure that I 1) have the money 2) get my pizzas and 3) they aren't poisonous or mislabelled.
The difference between "you can't blatantly lie" and "you have a fiduciary duty to act in your client's best interests" is enormous.