It may have been (probably was) a conscious choice illustrating how new things were (i.e. those people didn’t grow up typing to a level where it was muscle memory). Also, keyboard layouts on early machines were far from standardized (other than the qwerty letters, almost every other symbol was not in a standard location from machine to machine), so even if you knew one machine you might not know others.

Most actors and directors put a lot of thought into small details like this, so when you see something like this it’s often intentional.