I think this is something that varies with age. At 30, I was very aggressive in seeking better pay and more interesting opportunities. 20+ years later, I'm pretty much near the peak of my salary band in my region, and the work and environment is good enough to stay. I also have the typical roots put down; home, friends familiarity with my community. Disrupting that would be very stressful and the rewards would have to be commensurate.

So why would I bother jumping to a new job for a 10% increase?

I think the Great Resignation is really for industries that have had stereotypically low compensation, coupled with shitty environments. And I'm glad that people in those industries have a lot more leverage to make things better for themselves.