The usual story is that we are careless calculators. The better story is that we are careful about the wrong things. Notice how rarely anyone is argued out of the tip jar, and how often they are simply moved past it by a change in circumstance. The strange thing about the tip jar is not that it exists but that it works, most of the time, for most people. We describe the departure from the model as an error. We might equally describe the model as a hopeful guess about us.
The ordinary case
Nobody sets out to be governed by the tip jar, yet it shapes an astonishing share of the ordinary day. None of this is new. Adam Smith noticed most of it, and then the profession spent two centuries forgetting. The point is not that people are foolish. The point is that regret is expensive, and we economise on it like everything else. If you want to see regret at work, watch a queue form where there is no reason for one.
