Don't overlook the tough guys that want to crush your fingers.
I've run across a number of Mexicans who are extremely strong. But when I shook hands with them they just held out a limp hand for me to grasp, then took it quickly away. I suppose they don't believe in the ritual.
You know, I have noticed the same thing. I don't think it is because they don't believe in the ritual.
By the way, if you want to see serious handshaking, watch a few Navajo. A modestly firm grip, but it can just go on forever, especially if they've been out of touch for awhile.