I think a lot of times they just don't want to mess with a van even though they can handle it. When I book loads, I'm always sure to specify with the broker if the vehicle is not dock high so they can make sure with the shipper and receiver. I've booked loads that a dock high was requested but no other carriers responded to the load listing and the broker basically told the shipper that if they wanted their freight moved they would have to load a van. I've heard some colorful language at those places.
I've seen some pretty creative loading and unloading before, including the scenario Turtle mentioned with using a liftgate truck to bring a forklift outside. That was quite interesting to watch. The thing that burned me up one time was when I booked a brokered load from the bid board of another carrier that shall remain nameless and it was picking up at one of these UPS docks that is open in the middle and has the dock doors all around. The load was two skids, about 1800 lbs total, and when I was in the office getting the paperwork I asked where he wanted me for loading. The guy gave me a door number and I replied that I wasn't dock high and asked him where the ramp was. He replied, "We don't have a ramp. Go to door 14 and I'll have someone help you load it." So I went to door 14 and someone brought the skids over and I proceeded to break both of them down and load them by hand onto skids I had placed inside the van. This took a while since both skids consisted of a very large number of small boxes. I finally got everything on board and when I was pulling around the building to exit the premises, I noticed a ramp on the corner of the building. I went right back inside and gave the manager a pretty good piece of my mind. Yeah, I know, I probably shouldn't have done that, but I wasn't too happy since it was about 95 outside that day and I was sweating from head to toe from loading all that by hand.
I told the guy that I had half a mind to increase my rate for the extra effort, especially since they had a ramp and he just sat there without saying a word. I then told him that I was going to go out and come back in with an invoice and he told me that wouldn't do any good since he didn't have the authority to authorize any additional payment. After that, I called the other carrier that shall remain nameless (meow) and told them the situation since they were the ones I had gotten the load from. They turned around and made a couple calls, then called me back and said they were adding $75 to my rate just for my effort. Since they are a larger carrier than I am, (I think they have a couple more trucks than I do.) and since this was one of their major accounts, I guess it was easier for them to get extra money out of it than it would have been for me being a third party carrier as far as they were concerned. Looking back, I think I probably could have handled it better, but all's well that ends well.