My brother in law collects Allis Chambers tractors. He now has 18 different, and a couple for spare parts. If he can explain why to a non collector, then coins, notes, maybe even tokens are explainable.
All sorts of people collect something, possibly more collect something than don't collect at all.
Think of people you have met that collect. Beer cans, tractors, Coke signs, pop bottles, Royal Dalton, paintings, blacksmith tools, stamps, sports trivia, and a whole host of "usless" items except to others on the same wave length.
Rick