My view is that the best way to think of it is as a personal service like a high end hair salon. Yes, it is business on both sides but treating your stylist or customer well makes the exchange pleasant and encourages better future business on both sides.
I took Mr. Smith as stating that just don't forget on both sides that it is just a "haircut". Nothing more. He didn't imply to me that one should not be friendly nor that extra gifts are bad. Just don't think that it was an emotional exchange beyond a friendly business relationship.