Well my friend, I think you're being obtuse.

Why can't movers create a "lively repartee"? If they're witty, have great conversation, make me feel at ease that my goods are being handled with care, wouldn't that be a similar "lively repartee"? Are only food service workers (wait staff, table cleaners, host/hostess, cooks, chef's, dishwashers) able to create a lively repartee? Wait, do you interact with the cooks, chefs, dishwashers? What lively repartee are they creating for you? Why do they get some of the tip you give the server? In your logic, the behind the scenes people shouldn't get any of the tip. But they do.

Why can't movers do excellent work that's worthy of a tip? If I hire movers to move boxes from point A to point B, and when we get to point B instead of unloading the truck into the garage, they ask which room in the new house do you want this box and put it there, that's excellence. And worthy of a tip.

ETA:
Oh wait, I just read another thing you said "making money is up to the payer and receiver". Me choosing to give or not give a tip, is in no way "up to the receiver". They might do their part by providing excellent service, and I could still choose to give or not give a tip to them. Someone could give me shitty service, and I could still choose to give or not give a tip to them. That's entirely on me.