This past week I discovered two jobs where one is forced to receive extra money just for doing their job (and it's not a bribe)
First is for workers at the harbour/ports. Even honest people walk away with (a minimum) Kshs. 2,000 at the end of the day in lunch money from grateful transporters just for doing their job. These guys (transporters) pay so many bribes that when someone does their job without asking for a bribe, they still can't get over that and press some cash into the reluctant hands of the officers.
Then, passing through the airport yesterday, I overhead several travelers, too bothered to reprice the cost of a cup of coffee in Kenya shillings, pay 1 or 2 dollars or pounds and dash off to their gate. How that money is shared is another matter – but when an 80 shillings soda is paid for with a £1 note (equivalent) to about 130 shillings, there's a healthy cut for someone – and probably more than any tip jar would bring in. This is probably a common occurrence in in the tourism industry (see how tour van drivers usually have plenty of dollars to sell)