Maybe it's just you cherrypicking examples. Just as you think we are discourage tinkering, I can point to the DIY and Maker movement, the proliberation of Hackerspaces, and so much more.

In any case, humans do not build a civilization by having really smart men who know everything, but having specialists in all area of life.

The scientists would do well not to express their disgust and disdain for the lowly plumbers or the trashmen,

Yes, we are stupid, but so are you. Just pick an area that you know nothing about.