Apples and Oranges. Trailer tires (specifically the sidewalls) are more robust.
I see a crack where your finger is on picture #32. I don't understand not spending $40 for safety and piece of mind.
Not around here they're not. They're usually some junkyard tire that has been baking in the sun for 20 years that happens to fit whatever rusty rim will also fit the bolt holes on the trailer. Usually hauling a load of trash down the local 4 lane road.
And, maybe he doesn't have the $40, to some people that's a lot of money when its an unexpected expense. If I were in the position where it was either pay a bill or buy a new tire, I'm paying the bills and trying to save for a tire while I'm keeping tabs on the air and driving back and forth to work/store/necessities.
Everything in life is a risk, you try to mitigate the best you can, but sometimes you just have to stare it down and get on with life and hope things hold together long enough to make it right.