Because they truly didn't believe the world could continue to function without them.
Just like many bureaucratic agencies today. Which brings it around 360* to the OP, where the FAA is threatening to close or cut back lots of towers, and the reaction from many of us is "meh".
And their greatest fear is (as expressed by some senior government executives) that the citizenry will realize that the government CAN be cut, and substantially, without significant impact.
Agreed.........