The need for a CDL is one obvious reason. It looks like the internet disagrees on whether CDL requirements start at class 6 or 7, so we're really only talking a

The need for a CDL is one obvious reason. It looks like the internet disagrees on whether CDL requirements start at class 6 or 7, so we're really only talking about 1-5. And I've definitely seen 4s and 5s on the highway that have probably never seen a spec of dirt in their life. So there are certainly some people just looking to get the biggest thing they can legally drive.