No, not unless there’s a specific agreement to do so. It’s something that is customarily done in certain industries and/or under certain circumstances, but ultimately it’s simply a voluntary “deal” between the company and the exiting employee. The company says, essentially, “We’ll pay you X dollars if you’ll ‘go away quietly.’” And if the employee says “OK,” the two sides have a deal. If the company chooses not to make the offer, they save the severance payment, but they take the risk of getting sued if you have a claim against the company.