People are notoriously ruthless to people who admit their mistakes. For example, if you are in an argument and you lose (whether through poor debate or your argument is plain wrong), and you *admit it*, people don't look back at it as a point of humility - they look at it as a reason to dog pile on you and make sure everyone knows you were wrong.
In this case, it's not internet points - it's their jobs, and a lot of money, and massive reputation - on the line. If there is extreme risk and minimal, if any, reward for showing humility, why wouldn't you double down and at least try to win your fight?
People are notoriously ruthless to people who admit their mistakes. For example, if you are in an argument and you lose (whether through poor debate or your argument is plain wrong), and you *admit it*, people don't look back at it as a point of humility - they look at it as a reason to dog pile on you and make sure everyone knows you were wrong.
In this case, it's not internet points - it's their jobs, and a lot of money, and massive reputation - on the line. If there is extreme risk and minimal, if any, reward for showing humility, why wouldn't you double down and at least try to win your fight?