You are missing the point @OP. For many people, what you say rings true, but not for everyone.
The grass is not always greener. You may find, like I had, the perfect position with the perfect manager and the perfect coworkers in the perfect company. Sooner or later, your coworkers will leave or get promoted, same with your manager. The company may be bought by another one, or a change in leadership will change the company values. And that perfect job becomes a mediocre, stressful and boring job.
In my personal experience, you may get a couple of years in the perfect job, then sh-t happens. You may jump around, like I did many times, but the older you get, the harder is to jump ship.
FMC was one of those perfect jobs I mentioned. After a couple of years working here, I got a new LL6, and he was one of the worst managers I ever have. The team scattered away, because people didn't want to deal with that sh---y manager. Yeap! Said goodbye to that perfect job. Even when the manager went away (promoted), the team was broken.
I am eyeing retirement, and age is starting to be the main obstacle to jump ship. Sure, I can still find a job, but I cannot command the same salary. So I am staying at FMC, increasing my savings, and preparing for retirement.