Talking with customers - a reminder

I have two little kids who attend kindergarten. Today I wanted to pay for a whole month. The lady flipped through a few printed spreadsheets of data to find out how much I should pay. It took her about 15 seconds, and then I paid in cash.

By reflex, I asked:
"Wouldn't it be great to have a computer find that amount for you."

To my surprise, she replied:
"Not really. But you know what would be great? If people could pay by card. We accept cash only. And I constantly don't have cash for change."

Now, I have no intention of writing software for kindergarten, but this simple experience has reminded me how my mind looks for solutions and how far it can be from where the actual problems that people care about are.