I would say it’s unusual. Most places I’ve worked, it was more or less a bimodal distribution: lots and lots of people with tenures of less than 5 years, a bunch execs and highly paid in-crowd folks who were there for 15+ years, and a vast emptiness of people with 5-15 years in company.

I think a lot of people leave as soon as their stock vests (3-4 years) and it’s obvious they are not on an upward track. And the few who got on to the upward tracks are set for life and have no incentive to leave ever. There’s no middle ground.