That said, my experience is primarily anecedotal; people I know who own only a truck, dealers who are selling trucks, and various reader survey type "Why buy a truck" articles that show up in the popular press like Popular Mechanics or Car & Driver from time to time.
You have focused on the actual need versus the perceived need. The aforementioned dealers are big on selling the "unknown future need" and the fear of finding yourself in a position where having the truck would solve your problem but you don't have one.
Like your argument above, I tend to be much more analytical in my purchases and so I like to believe I am not influenced as strongly by the "what if ..." arguments. (It must have some effect since I don't own a pickup truck at the moment :-). I have also learned, that precision thinking isn't always the dominant force in a lot of buyers making buying decisions. I encourage anyone thinking about this question to talk to truck owners and ask them what they were thinking when they bought their truck and how much of how they anticipated using it was something they actually did post purchase.
I've moved myself and a number of friends using just my mid-sized pick-up.
Moving apartments and similar activities are (a) rare; (b) can't be done in a pickup anyway - I'd need to rent a much larger truck; and (c) renting a proper truck every time I moved and will move apartments/houses in my whole life is cheaper than the cost difference between a pickup and a smaller car, especially as fuel is a huge part of total cost of ownership.