I worked preload for about a week as a seasonal driver. Then worked the next years season as a seasonal driver as well. Called them up in June and asked if they needed any help. They offered preload; I was like "no thanks. If you have a driver position open up just let me know thanks". They called me the next day. I've been driving since. I have my own bid route now. Good timing, and putting a little ultimatum in helped me stay away from preload. Not to mention 100 clicks under daily when I drove seasonal. I knew what they wanted. A kiss ass that would work for them and fast. Now I'm like 100-200 clicks over daily. Working as directed. But safe as well.
Put yourself in their shoes for a second. When they have 100 people crying to them daily and half of those don't want to do the job correctly or abuse union protection. Then reevaluate yourself. Are you one of those? That would probably be why you don't move on.