That's exactly what would happen "if all the major shippers and receivers refuse to pull the pallets to the rear or push them forward." Cargo vans and Sprinters would be obsolete, as shippers would only consider dock-high vehicles for their needs to make things consistent. They wouldn't even consider the odd Sprinter or Box truck with a roller deck, because there simply wouldn't be enough of them to mess with, much less enough to fill the need. And a roller deck on a cargo van would eliminate all 48" tall pallets, severely limiting them in what they can haul, to the point where it wouldn't even be profitable in any way to be in the business with a cargo van.
I've been doing this a while now and I've never had even one instance where a forklift driver balked at pulling a second pallet towards the rear. That tells me that whose who do refuse to pull them are the very rare exception rather than the rule. And I've never heard or read anything that indicates otherwise.
Most expedite contracts specify the shipper loads and the receiver unloads. Some even expressly prohibit the driver from handling the freight. It's the customer's freight, and it's generally up to them to figure out how to load and unload it. If they want to transfer that responsibility to the driver, without any of the liability, that's also on them. Otherwise, it's up to the customer and dispatch on what they want to do, be it pulling the freight out, a cross dock, or even placing a pallet jack into the van to pull the freight towards the rear (which I've experienced a couple of times due to really odd circumstances, like them not having a fork truck, but only a hand-operated power lift).
If I get to a consignee and they refuse to pull the a second pallet out, then I would call dispatch, who calls the customer, and someone other than me makes the call on what to do.
"Banning the Van" would suit OSHA and The Government fine as they would love to get us all tangled in their logbook, HOS, Weigh Station harassment web.
If they wanted us tangled up in their logbook, HOS and Weigh Station web, we'd already be in there. We're not in there because they don't want us in there.