Every single person I know well has a double standard for something. Such as “I don’t need to improve my driving but everyone else sure does” or a “do as I say not as I do” rule, etc. Though certainly some more than other. This leads me to believe all people do it in some way.
Is it simply human nature?
Have you ever met someone like the people you want everyone to act like? I have. Many times. They are usually either SUPER neurotic or very rigid and extremely unforgiving of themselves when they don’t meet their own standards. Everyone bitches about them or pathologizes them. So no it’s not human nature because humans are not a monolith with default behaviors.