Earlier quoted context omitted.
That too. Though that is a much more nuanced issue with a lot of arguments on both sides.
not as nuanced as all that as an employee, if you are lucky/skilled enough to end up at a successful startup, and you aren't very careful with tax issues, you can find yourself stuck: if you leave, you have to exercise, and immediately owe hundreds of thousands of dollars (or more!) on a completely illiquid asset that you can't sell. Which doesn't even take into account the potential for that asset to become less val…
And if one person leaves it's not likely to materially affect the business as everyone else keeps it going.
Another point of view is that if all the early employees disappear at the 4 year mark (or whenever they feel they've vested "enough") that could cause very serious problems for the business. There is an element of a prisoner's dilemma here and it's not unreasonable to think about ways to keep people from defecting.
As I said, it's complicated.