This is a fake world. In the real world there is history, capital and labor, and politics which is an expression of the unavoidable, built-in antagonism between the two. We don't all own an equal share of the means of production and just sit around issuing contracts to each other all day.
Do you understand that the econ 101 libertarian world of homo economicus rational agents is fake and we live instead in the real world with its institutions and conflicts?