Obviously congressional staffers are only a small part of the federal workforce, but the dirty little secret of Washington is that the country is run by poorly paid 25 year olds. Washington is an expensive city. Low level staff jobs really don't pay enough* unless you have some sort of parental support and backup, and of course such jobs are stepping stones to other careers in various corridors of power. In other words, only people of a certain class will tend to take such jobs and move into positions of real power.
*They might pay enough that you can afford the austere life in the several roommate flophouse, if you don't have tens of thousands of student loans to repay, but these just aren't high paying jobs given DC rents.
