They are less disposable than regular cars because they can be used for more things. Most people have no use for a 25 year old passenger car that runs but is in poor condition, it will get you from point a to b and thats it. Many people have uses for a 25+ year old truck that runs but is in poor condition. It will get you from point A to B, AND: haul heavy dirty stuff in the bed, haul heavy dirty stuff on a trailer, drive over terrain, pull stumps, plow snow etc etc etc all in one vehicle. This is reflected in their pricing, a 90s ford escort is worth scrap, a 90s f150 will still fetch at least a couple grand or more.