I think this is true unless you're hauling something that you really don't want in a closed space with you. Lawn equipment, motorcycle, fertilizer, that sort of thing.
I think in America we'd just call that a "flat bed truck" or something, which is a catch all for those that do indeed have flat beds as well as these with short sides around the bed.
That got me there with a little extra searching. "Flatbeds with side gates."
Here they are very common on construction sites for the messier work (building roads, railways, walls, roofs, forestry etc) but normal vans with a roof are more common for the cleaner work (plumbing, electrics, painting, carpentry etc).
* protects your goods from weather
* more cargo volume
* better forward visibility without a long hood
* easier to load and unload due to being lower
* can park it without people being able to walk up to it and taking your tools and equipment out of the exposed truck bed