The History of Airport Security
Annie Wu at The Savvy Traveler - passengers have been searched for weapons before boarding flights only since 1972. Before then, you could carry anything you wanted on board, and, if it was hidden in your carry on bags, nobody would know. A few hijackings and bomb threats were all it took to give the goons permission to grope us at will.
Personally, I think it should be up to the airlines how much security they provide. If they think disarming passengers will enhance their bottom line, they'll search them. Otherwise, not. Let the market decide.