In our culture asking what work people do is not impolite. Asking someone's age would become more impolite the older that the person being asked is. So it would be very acceptable for someone in their teens or 20's, would be become possibly unacceptable to a person in 40's or 50's, and would depend on the person if they were older. Asking about someone's income would usually be thought of as impolite. All of these customs are less important the younger the person, so kids don't worry about any of it.