Because such entities, even when acting in the public good, would be breaking the law if they did. Those who publicly act in the public good usually try not to break the law to do so.
EOs cannot violate the law, or compel someone to violate the law. Could the president issue such an executive order? Potentially. But that does not mean it gets carried out, or is legal.
Do you think this president would? I don't think it terribly likely, and if I heard that he was about to, I'd probably start booting Linux for a few months, because I would wholeheartedly suspect that it did more than just patch effected systems.