That's because they hold on to the banisters!
I once met a family with one of those 5 button shabbas locks in their door. The problem is that over the years the three buttons in their code got so worn down that it was blindingly obvious which buttons to use. Given the way these locks work, there are only 6 possible combinations to choose from. Whoops.
Ha! Unless they had a different combination, and got a trick "looks worn out" lock.