As someone who works for a major healthcare company - they hire doctors so they can claim to have legitimacy in denying claims. If their doctors say that something is "unnecessary" or there is an alternative, it's better for legal purposes than just any old person saying it. Even though we all know those doctors aren't the ones in charge and are most likely pushed by the people above to make certain decisions.

There are countries where you cannot fire people just because they got sick. In those countries you'd have to keep paying the sick people and it becomes cost effective to employ a doctor to help them get to work again.