Because usually they get paid to 'clean the car' which means they have a whale of a time with the hose and some soapy water and the car ends up looking a bit shinier in places, but no-one removes the sweet wrappers, dead grass and bits of misplaced lego all over the inside.
So this time I am paying them to clean the inside. The payment for this job is ... that they then get to clean the outside (and an icecream).
DD thinks I am being mean. I think it's sensible workplace management. And they've gone for it. Result! 