[chengas123]

So it's immoral not to follow societal norms? Is it immoral to have a pink mohawk?

I think you're right that there can be implicit agreements in place such as the agreement to tip your waiter. The waiter example is quite different because you've made an implicit agreement. The point of a contract is to leave nothing implicit.

Also, part of the confusion here is that there is no precedence to say what the societal norm is. Housing prices have never fallen this much before in our society.