Andrew Thompson in Engineers of Addiction, a fascinating profile on the psychology of slot machines:

Game [slot machine] designers are charged with somehow summoning the ineffable allure of electronic spectacle — developing a system that is both simple and endlessly engaging, a machine to pull and trap players into a finely tuned cycle of risk and reward that keeps them glued to the seat for hours, their pockets slowly but inevitably emptying.

In other words, their job description is to make people win just enough so that they come back long enough to lose big. I just can’t wrap my head around that.