Design for the product's average user
A good piece of advise is to design for the product's average user.
If you are designing for the Blumberg Terminal, feel free to include whatever complex hidden keyboard shortcuts you like. Those users like that kinda of stuff.
If you are designing a public washroom in a downtown restaurant, assume the user has sat on a toilet before.
Do not label the soap. "Hand Washing Soap".
This label adds nothing. It only creates distraction. Over the course of time, this small misstep will waste hundreds of hours of precious human brainwave activity with its meaningless three words.
The label's edge will eventually attract mold and muck. Its adhesives will fail and it will flop.
P.S. It's off centre.
P.P.S. Designing the soap button with an 'indent', is the perfect way for water to always pool on the button so that it can most effectively grow bacteria.
P.P.P.S. Designing the soap level indicator as a large plastic outgrowth is the perfect place for bacteria to thrive.