I think a lot of the rust that some rigs suffer from is from clogged up drain holes and dirt sitting on the backside of things.
If you compare some trucks that have been in the same area all thier life, one has waisted doors and boxsides the one next to it is perfect. My ‘98 Cummins 400k miles lived its life here in Spokane with heavy snow and deicer never garaged, never had rust. I know of plenty that have. Some body styles it’s how it was washed. I think some are worse then others for having bad designs where dirt can collect and be hard to clean out.
As far as cars having s***ty metal, yes there are different qualities of steel but regardless of what people think steel has continued to get much better quality since the ol cars people refer to, more rust resistance and stronger however it is thinner.
