It's... just life. e.g. it is not only trucks - it is the same with SUVs, and Jeeps. I heard (no idea if it is true) that the original Jeeps were brought home from like the Korean/Vietnam wars, and were still military style, like had like zero padding on the seats, much less windows or AC.

People also wear clothing in a similar manner too - how many people wear cargo shorts while not hiking, or active/fit-wear while just loafing around. Billionaires purchase yachts and then they literally never leave the harbor. Trump has a literal model wife, who it seems he is never allowed to touch. People purchase iPhones, and then use it as a phone but never listen to any music from it.

Given the luxuries available today, people purchase things based on "how it makes them feel", rather than whatever it was originally meant for. Trucks are a symbol of independence - like, "I could move a large furniture item - I never have and I never will, but I could, and I like how that makes me feel! Also I tower over all ya'all and I enjoy how I block the fucking road so that you can't see past me when I'm 5 feet past the line and you cannot make the turn that you legally should have been allowed to if it were not for this mobile obstruction blocking the fucking roadways... um, [cough], I mean I like it."

Mine's a beat to hell 2004 F150. It's for doing nasty truck work. I've never washed it. Besides, no one's looking to rob that POS!