Thankfully most truck owners fall into the:
A: Don't got shit in the bed ever.
B: Always got shit in the bed, cuz I'm too lazy to unload it all the time.
The C: Often vary load by hundred of pounds through the course of the week catagory is rare. Perhaps most common in landscapers who occasionally haul dirt/material that is then unloaded and empty till the next job.
Construction folks are usually in B. Suburbanites and most of the jacked up country trucks are A:.