We actually see this question more frequently than I would guess. The fact is, we rarely have these conversations. About as much as you would ever get is, upon putting on a pair of glasses:
"Oh, are you a bit nearsighted?"
"No, I'm super nearsighted. Can barely see my hand in front of my face without my glasses."
"Just a little - I only wear my glasses to drive"
"No, I"m farsighted - I need reading glasses for close-up work, but that's about it."
I actually do know how many diopters my lenses are, but that number would be meaningless to most people.