wow.. my truck never has 'nothing' in it.
I carry tools and equipment that would 100% fill the trunk in a small to medium car. need em for work.
I also carry some extra clothes and a few items i might need on long weekends. Both my jobs are away from my house / farm.. so I have to have stuff with me. Car just wouldn't do it.
Besides. never know when you will pass a yard sale.. or farm sale.. or auction.. and need a vehicle big enough to set 2 tractor tires int he back, along with your 3 tool boxes. :)