The stranger category is the surprising one. A receptionist who spends nine minutes hunting down a cancellation. A driver who waits with the engine off until you are through the door. Somebody at a bus stop who just moves along the bench.
None of them know anything about your situation. They are not doing it for you personally, which is exactly what makes it worth counting — the goodwill was already in circulation before you needed any of it.
Friends and family get thanked. The rest of it passes without a receipt, and it is doing a quiet amount of the carrying.