It costs more but it's also likely to break often and would be a liability. The tray could snap off or a finger could get stuck in it. How annoying would it be

It costs more but it's also likely to break often and would be a liability. The tray could snap off or a finger could get stuck in it. How annoying would it be if the machine is constantly out of order? A machine that deals with the general public on a scale of tens of millions has to be rock solid. People can behave really strangely (think drunk people) and all kinds of ridiculous outcomes can happen.