Many JWs feel that since the servers are worldly, and therefore already dead in God's eyes, that it's a waste of $ to tip them since these sinful pagans will soon be throwing their gold and silver into the streets, and their eyes will be rotting their very sockets.....
Another habit JWs have is, if you offer to take someone out to a restaurant, they always order the most expensive things on the menu. However when they have people over to their home for a meal, they serve macaroni and cheese.