It's a logical assumption, for the obvious reasons, since fleet van driver turnover is going to be higher than that of straight and big trucks, anyway. But Panther has a rather unique culture with regard to its van fleet owners. They cater more to the fleet owner than they do to the drivers. They encourage van fleet owners to expand, assuring owners that Panther can find warm bodies to place in the vans, which discourages thorough interviews by the owners since Panther has done all the grunt work. They have policies in place to deal with the lowest common denominator (the clueless van driver making no money with no investment in the vehicle) that are explained to the van O/O but are not to the van driver.
When the van driver has questions about some of the details, especially confusions or disputes in pay, the standard reply is "talk to your owner" because they won't talk to the driver about pay issues, as the drivers are paid by the owner, not Panther. The owner isn't running the loads, so they don't know the details of the dispute either in most cases. For example, when a driver negotiates a bonus or some other accessorial that doesn't get paid, they won't talk to the driver about money, that's between the driver and the owner. The owner doesn't know what it going on with it, so they have no knowledge with which to go to bat for the driver. The driver is left feeling that either Panther or the owner is cheating them.
Panther deals with van fleet drivers more like they are employees rather than respected business owners. In their view, the drivers are leased to the owner, and Panther will only answer to the owner. I saw that first hand because of the unique situation I was in when I was with them. The van's title was in my stepdad's name (not anymore, but it was then) and he was technically the van owner and I was his driver. My stepdad didn't want anything to do with it at all. He's old and has a lot on his plate as it is. Papers were signed, including full power of attorney, instructing Panther to deal directly with me on any and all issues. I was also the only driver at Panther who had the Comdata Owner Card on the driver's screen who wasn't technically the owner, which made for some interesting "whoops" moments. I got a lot of "Talk with your owner if you have any problems with it," kind of thing. Once they realized they had to deal with me directly on the issues, attitudes changed dramatically. They became more responsive and forthcoming with details, and disputes were settled quicker and easier, because they had no choice but to deal with it.
These types of things, and other factors, result in even higher turnover than one would find with van fleets in general.