This is probably true, but i still feel like the average trucker is at least as courteous as the average car driver. The problem is that if a trucker messes up, everyone else is in worse shape, because trucks are so damn heavy.
I’m just talking about over time. In the 1980s and 1990s most trucks were being operated by large companies. Trucking companies like Yellow, Roadway, Consolidated Freightways, Arkansas’s Best or big distributors and retailers, Kmart, Kroger, Safeway, SuperValu, Sysco, C&S. Often unionized.
Now a huge part of the market has shifted to decentralized owner operators bidding for jobs through brokers. Kind of like Uber & Lyft or DoorDash. While the big players have deep pockets and a motivation to monitor the behavior of truckers, the mom & pop operators (sometimes literally husband and wife teams) are engaged in a race to the bottom.
I once knew an apprentice actuary who quit to go into long haul trucking with her husband. 
My guess is they aren’t racing anyone to the bottom. But they may not be representative.
Does Covenant still put large “It Is Not A Choice, It Is A Child” stickers on the back of their trailers?