Continuing the theme, many police actually take indirect bribes. Look up Patrolmen's Benevolent Association cards and the like. There are different levels of tokens depending on connectedness and donation level, and you can find them openly discussed on police forums. I would guess the only reason we haven't developed a culture of on the spot cash bribes is that police would take the money and write you a ticket anyway for having insulted them. They have a psychological need to pretend they are on the right side of the law.