Yea, freight companies have to comply with the FARs . . . the problem is a lot of the time they DON'T and the FAA doesn't give a damn unless there's an accident or incident. I'm convinced that there's often a cozy relationship many times between the company and the POI & PMI.
The truth is that the freight companies' quality varies widely. Good companies like FEDEX, UPS, Atlas, etc. do a good job of taking care of their airplanes and crews and complying with regulations.
If you want to see the real scum, take a look at some of the so-called 36th Street freight outfits flying out of Miami or the small freight operators flying the light twins, etc. The problem is the managements will NEVER allow you an unfettered behind the scenes look, nor will the crews, for obvious reasons. You'll find the most colorful crews working for these guys. Some interesting personalities and lots and lots of stories to tell.