Pickup trucks are used by people who need to carry or tow large items such as wood, appliances, trees, other pickup trucks, cars, horses, cows (though towing livestock required a special type of trailer) lumbar, farm tractors, farming equipment, construction equipment, small construction machinery and the list could go on and on.
Yes I realise that, but do many Americans (especially ones who don't live in rural areas) actually need to transport all those things? There can only be so many farmers and construction workers but a huge number of Americans own pickups for private use (rather than as a company vehicle). Maybe it's a cultural thing, some Americans seem to live closer to the elements than British people (America is a land of huge forests and vast areas of countryside, most of England is already built upon) not many people in England drive pickups (although these big Nissan Navaras are becoming quite popular) and I don't any think European car companies actually make pickup trucks, the pickup trucks you see in England are from Japanese makes like Mitsubishi and Nissan.
To me the main disadvantage of pickups is the single cabs don't seem to have much passenger space, and when a pickup is a double cab they become absolutely enormous (some of them seem even bigger than SUVs). Anyway I still don't get why so many Americans seem to love pickup trucks (America really seems to have a long-lasting love affair with the pickup), I wouldn't want to drive one around (unless I actually needed to carry something) anymore than I'd want to drive a transit van. That's how I see pickup trucks, they are just a goods vehicle like a van or a lorry rather than something that is aesthetically pleasing like a nice car, so why some people actually find them attractive and want to drive them everywhere is beyond me. I have come to understand why some people like SUVs (even though I still hate SUVs and I disagree with those people's tastes) but I haven't worked out the appeal of the pickup truck, but then I never actually lived in America.