[irrational]

You must not be familiar with tipping. Tipping always happens to people with no power. Bribery happens to people with power. Nothing bad will happen to me if I never tip (other than perhaps bad karma and some dirty looks). Very bad things can happen to me if I done give bribes. Tipping happens after the service and payment are completed. Bribing happens beforehand. The two are so entirely different on almost every level (especially the power dynamics).