People in basic jobs can still compromise security of the facility.

People in basic jobs at Twitter helped murder a journalist.

Secure facilities still need janitors, plumbers, electricians other maintenance people. I worked in a downtown data center that did banking and securities trading and had to badge through three doors to get to my desk. Every night a different janitor I'd never seen before would also badge through both of those doors and empty every trash bin on the floor, and then another person would come in around 3am and vacuum the whole floor for two hours. Based on the rate that new people cycled through those jobs I doubt they were being vetted very hard.