Why do we bother making {lying, stealing, killing} illegal, when we could just rely on people to have the agency to avoid getting hit?
Because we live in a civilization.
Because we live in a civilization.
A better example is this:
Someone goes into a used car lot and explains to the dealer that they live in a cold climate with lots of snow, have three kids, and go camping a lot. They explain that they need a car with lots of cargo room, is reliable, cheap to maintain, and which is good in icy conditions.
The dealer proceeds to talk the buyer into buying a 20 year old porsche 911. It doesn't satisfy any of the stated needs and costs the buyer money that they didn't need to spend. The dealer's actions were clearly unethical. But, should they be illegal? Thats a very complex question and not one that can be answered by "MOAR REGULATION!" demands.
If the dealer lied about the car while selling it, then in theory the buyer can successfully sue for damages. In practice it's likely to be hard to prove.