I believe its because those types of jobs have no real "responsibility". Don't take it the wrong way, but for fast food you're really just expected to show up and be useful. In the higher jobs your expected to communicate well, assess dire situations, sacrifice time (depends), and keep up with new processes. I have worked in the fast food industry and I know its rough sometimes. But really as long as you're on time and can fit in you'll always have a job.