This is something that has been a problem in the trucking industry for years. Some shippers, receivers, and even trucking companies view the drivers as slave labor and expect them to do the loading and unloading.
There are laws against this sort of thing but they aren't enforced and far too many drivers just do it. Not me.
Some trucking companies get around the law by paying the driver a small amount, something like $25 or $30 to do it, when they'll pay a lumper service (unloading service) $150 or more to unload the same freight.
My pat answer is simple. CDL doesn't stand for Combination Driver Lumper. I drive the rig, I don't load/unload freight. Not my job.