Occupations/Insanely firm handshakes

I used to live in a city that was the home base of a leading overnight shipping service.

And I met a lot of pilots. One thing I noticed about them was the fact that a seemingly high percentage had what I would call unnecessarily firm handshakes.

You know what I’m talking about. The kind of handshakes that feel more like an assault than a greeting. (Even if you yourself are quite capable of squeezing someone’s hand robustly, you are at a competitive disadvantage when the other person catches you off guard with the vise-grip of doom.)

I don’t recall associating other occupations with this habit, though surely pilots aren’t the only ones who do this. (And I realize not all aviators do.)

I knew a sweet old guy who used to really pour it on when we met. But I always chalked up his firm grip to enthusiasm. He was a retired wheat farmer.

What has your experience been? Have you found any correlation between occupation and handshake vigor?