I think the fuel consumption thing is a bit of a red herring. I doubt ther will be a huge difference between a car towing a van at 50mph and an unladen car at 60 mph. Plus, in my case anyway, if we are towing the van, we are usually together, that is in one car wheras we would normally be driving two cars to different locations.

Insurance - well, as Richard says, almost everyone would insure their van simply because of its replacenment cost, but i accept that some people don't, much the same way as some drivers don't insure their cars.