Its a standard thing to acknowledge a thank you, especially if the dude is working for tips. The guys comes around, hands over a glass of lemonade and walks away like I was not there. Niggas like that are taught by the corporate trainers to do shit like that, that's the 1st thing they are taught is to smile and be thankful, and the dude should've been double thankful that I thanked him on his not-so-fast service of bringing me a tumbler half-full of lemonade. 90 seconds before I stiffed him, he asked how was the service, and I told him "It was good!", [but it wasn't great!].