Sure, it's easy unless:

* You are dependent on your employer for your work visa; * You are dependent on your employer for your health insurance (US-specific problem); * You have don't have much experience in industry and thus will not easily be able to find a similar job; * You don't have enough savings to be able to be unemployed for a period of time while you find another job (doubly so if you have dependents or you have a non-compete agreement which would make you unemployable for a significant amount of time); * You have a criminal record that makes hiring far more difficult; or * There are few competitors in the space where you have expertise (or the few competitors you do have wouldn't hire you for one reason or another).

There is a very large number of people which would fall under at least one of the above points.

Yeah, yeah, the right of exit and all that. But that's still overlooking that companies, especially the most successful ones, start to resemble the exact same kind of institutions that those who are the most pro-private sector decry.