Great, but what has that do with your initial point, that employers are somehow bound by law to pay PTO, severance etc.? When they file bankruptcy you end with empty hands, unless the company decides to gracefully shutdown before they can't pay you anymore. In a fairytale cloudcastle world that's how sound bussinessmen should take action no doubt, but here in reality companies usually give fuck all about their employees.
Sure, there will be some litigiations down the road, but when the company simply has no assets to liquidate anymore or in the ever more popular scenario that the heads ran off with the money, you won't get anything. And even if there's something left to liquidate you will receive your outstanding payments many months later and probably not even get all the money. Especially for people with families this is unacceptable.