The point is not that people are foolish. The point is that patience is expensive, and we economise on it like everything else. If you want to see patience at work, watch a queue form where there is no reason for one. Notice how rarely anyone is argued out of the free sample, and how often they are simply moved past it by a change in circumstance. The lesson is modest. Build for the person who exists, not the one in the model.
Three kinds of mistake
The usual story is that we are careless calculators. The better story is that we are careful about the wrong things. Ask most people why they did what they did and they will give you a reason; ask them again a week later and the reason will have quietly changed. A pattern this consistent is not a character flaw. It is a design feature, and design features can be worked with. Every one of us runs the same shortcut, and every one of us believes we are the exception.
