sniffnoy | I can't actually say anything sensible on the topic, so let me just ask the question

Why do we not teach kids to think properly about dimensioned quantities at any point during their schooling? Well, OK, that's an easy one, it's for the same reason we don't teach them lots of other stuff. My real question is: Why do people who surely must know how to properly think about dimensioned quantities continue to write examples and exercises in ways that reinforce bad ways of thinking about them?