PIN entry supports muscle memory

Over time, entering a series of numbers into a keypad can become embedded in muscle memory. That is, you stop thinking about each number individually and instead rely on the memorized physical sequence of pressing the buttons.

The Wells Fargo web site supports this phenomenon by allowing users to enter their PIN on a virtual keypad:

There is a difference here of course: rather than using fingers to type, you are using a mouse. So it's not a direct translation of the physical experience.  Over time, do people  have difficulty remembering the numbers and instead just remember the movements? I would guess this is what lead Wells Fargo to add the keyboard to their web site—and that displaying the layout is enough of a physical reminder to help people enter their PIN correctly.