They have changed drastically in our lifetimes because of 9/11. You used to be able to simply go to whatever gate you want and then show your ticket and get on the airplane. This is all still evidenced by the design of airports such as charles de gaul or the one in berlin that just closed which both have annoying security addons that disrupt the design and flow of the original architecture. All of this security theater has simply added to the cost of running an airport. I doubt it makes any of us safer.