@ElsieD I think it's because kids almost universally like the meals you mention. Parents usually want their young children to eat without complaining or making a fuss. That enhances the parents' dining experience.
That said, when our family would go out to eat we kids would eat what mom and dad would eat (and make our own choices} not from a special kids menu. I don't recall seeing a kids' menu until fast food became a more common dining choice, especially for families.