The details of the severance package weren’t known until after they had agreed to stay. You also need to consider that many people are attached to a specific job and are strongly opposed to leaving due to specific benefits they might struggle to find elsewhere. Besides the H1B situation that many have wondered about, there are also things like health insurance. Depending on one’s health situation—particularly with children—you may be concerned about finding a new position at a company with a similar health plan before your severance runs out. COBRA is expensive.