Every time I visit a clinic, office or train station I notice how easy it is to figure out the PIN required to unlock the staff-only door by just watching an employee entering the restricted area.
I usually don't have to do anything, not even trying not to get caught, simply it's pretty easy to know the PIN from a decent distance because the keypad design in typical and everybody knows the location of the digits and which one corresponds to which square.
However I went to the bank and the keypad there had a different design which made it difficult to guess the PIN. What is the down side of this design? why don't we see it used in safes?