The question is always why someone is not perfectly happy with a workplace, and what alternatives they have available.

You may work in a large bureaucratic corporation, want to work somewhere more dynamic, but you also have adjusted to the large corp salary.

You may work at a cool startup, but wish for more time for your family, however the jobs offering a better work life balance are uninspiring.

Add to that it takes effort to leave, and less effort to stay, and you have a lot of people "choosing" to stay.

Yes, employers have inertia on their side. But for precisely that reason, sometimes mild irritants end up having disproportionate effects in getting people to leave in a "The Elves Leave Middle Earth" moment.

Many, perhaps most, people have some degree of gripe-age with their jobs. Many also have enough experience to realize that the grass isn't always greener and the devil you know may be preferable.

I said this about Google. And I left. No $ for you, at least for this case.