sounds quite stupid when you think about it.
The person taking care of your teeth is usually as important as the person taking care of your automobile. So why is there a differentiation? People take their cars
in for maintenance as many times as they get their teeth whitened.
I don't even think judging by occupation serves a purpose. Anyone who has a job is useful. Everyone serve a purpose - whether if it's to balance the goodness in the world with anarchy or to mop the floors to keep up a standard of cleanliness.