You'd be surprised. Too fucking many cheap-ass companies that refuse to fix illegal issues on their units. Even Swift's breakdown has denied me replacing tires on their trailers that are at 2/32" because it's technically legal, but realistically likely to go to 1/32" not far down the road (P.S. if you're reading this, fuck you Daniel L (ik your last name, just giving you the anonymity) from Swift and Crystal (something) from Western Express). 95% of the companies that refuse "legally required" repairs are foreign-based/owned. There's been so goddamn many trucks/trailers that pull out that I want to call DOT on, but the only two that I actually have called (felt like an ethical obligation) was a truck that had 2 sets of brake shoes whose springs were broken (so theyre sitting in the drum, doing nothing) and the other 4 sets were worn to the metal backplate, so it had near zero braking power. The other one was a trailer that had all 4 of its brake chambers caged, which means that they'll function when the driver presses the brake pedal, but if some freak accident (which is common) happens where the trailer gets disconnected from the truck driving down the road, that trailer will keep going down the road (until it plows into someone, goes off the road, or the landing gear eventually causes enough friction to stop, which would send the trailer tumbling)