I’ll just bet that when England went to decimal coinage instead of pounds, shillings and pence, that 99 percent of the kids in England after that lost the ability to do that!
It takes LOTS of practice and there is nothing that promotes practice as much as making sure you get the right change when you buy something!
It’s for the same reason that I oppose the whole metric system! If you can’t deal with there are 12 inches in a foot, you need a course in bonehead arithmetic instead of a new measuring system!!
Sorry, Fred, if I could see it written out like in this strip, I could do that, but I’m NOT good at holding numbers in my head while I try to figure out the answer all in my memory!