Not sure why this would surprise anyone. The presidents salary is $400K. Of course, there are perks and bonuses, but government service is not an occupation where people go to get rich.
People in government jobs usually have a different motivation than money. Sometimes it's security of a steady job, genuine desire to serve the country, or access to unrestricted funds/info for malfeasance. Any number of reasons.
All good points. For some reason the FBI/CIA seem like private sector to me. I do not really have an answer why, but they do.