I agree that that is true in the long-run, but there may be temporary circumstances where someone will bear some pain longer than they might otherwise... maybe they don't want to create a "job hopper" look on their resume, maybe they feel dedication to (some) of their colleagues, maybe it's a down economy and jobs are scarce in their market, etc. In either case, I contend that management should, ideally, be willing to accept that sometimes the required change is on their side.

That said, my experience is that poorly run companies usually don't seem to improve, and that the best option for an employee is usually to just leave, depending on any mitigating circumstances.