I suspect you're familiar with the old anti-joke, No Soap, Radio. I met a pragmatic variation of this joke in a men's room recently. This variation owes a lot to the ingenuity of Manufacturing Engineers, who have introduced countless innventions aimed at lowering the price of manufacturing or maintenance, a few tenths of a cent at time. (I shall have a little more to say about that topic in the near future.)
The case in point is a soap dispenser. First, maintenance cost is reduced by placing the soap in a plastic bag that's easy to slip into the dispenser when it is empty. Second, the cost of applying enough pressure to the soap to dispense it devolves entirely on the customer. Initially the pressure of the full bag is enough to make the soap flow smoothly when the dispense button is depressed. But after awhile the soap stops flowing and more pressure is needed. That's why the following words are emblazoned on the dispenser:
No Soap, Slide Bar.