> I don't really see the point of them.

Then you need to get our and do more real work of lots of different types. Exposed bed is often an advantage!

I have a welder, the safety instructions include "Never carry the gas tanks in an enclosed vehicle" -if there is a leak the gas tanks (nitrogen, argon, helium) can quickly displace the oxygen inside and I'll die before I know what happened.

Most things I carry don't need to be inside constantly. A little rain won't hurt anything, I wouldn't want to store anything outside but just a couple hours won't harm most things.

Also it is a lot easier to load things in a truck than a van. I can lift it over the sides (perhaps with a forklift). I can stand up in the back while arranging things - even when it is full I can stand upright.

I have used both trucks and vans to carry things over the years. Both are a compromise - and like all compromises there are negatives where something else would be better. Overall I fall on the truck is better side for what I do most often - but that is overall and I recognize there are good reasons some will choose something else.

The rear being exposed makes them bad at carrying things that need to be inside, but it makes them good at carrying things that should be outside.

Also they are much easier to load items with heavy machinery.

Tonneau covers on the bed work well.

Not going to load manure into the back of a minivan.