Most projectionists used to be union guys, and you needed special training to operate those big projectors. Now, it's often the guy working the concession stand.
I was lucky enough to know someone back in college who worked at a local theatre. It was a crackerbox compared to other screens in town, but being invited up to see the projection booth is an experience I'll always remember. I also learned how dangerous 35mm projector bulbs can be. ;)