These aren’t random numbers. They’re the credit or debit card pin numbers of the two people ahead of me in line and one on the next till, in the supermarket last night. I was quite surprised how obvious it was to read the pin numbers. All three simply clenched all fingers barring their first finger, which then stabbed down obviously on the relevant buttons.
This isn’t just a risk to cash, it’s a risk to safety. One more common form of card crime is watching the pin number then mugging someone for the card once they know the number.
The best system is to have all fingers on different numbers on the keyboard, both those you’ll press, and those you won’t, then apply a little pressure on the relevant keys, this makes it far more difficult to work out what number is being pressed.