I'd quite like to actually see what the rules are, but this is just a complex one. On the one hand, obviously the US military would probably have an easier time securing classified info if unreliable people aren't wandering through the building. On the other hand, the US people do benefit from random people wandering the building and would get more out of looser requirements on who can get in. Making it easy to keep information classified has always been a strategic error that has probably done a lot of damage to the US.