@astrochuck—
I have been an accountant for over 30 years, starting with mechanical calculators and progressing to electronic ones and that question has crept into my mind countless numbers of times!
I think your comment about the alphabetical layout on the rotary phone is spot on. When Western Electric and AT&T introduced the new-fangled “push-button” phone in the late 60’s or early 70’s they tried to design them to look like existing phones so that the transition would not be too radical for those of us in the workforce 35 years ago.
Keep in mind that the technically oriented geniuses at Bell Labs in those days did not have the highest regard for the general public and thought that anything too new would be beyond our capabilities.
Anyway, that is my take on this.
Good question;;
SRM