Hong Kong Buffet

Shocked I was shocked to have the manager ask my guest about leaving a tip. Who asks a patron to leave a tip? Tips are earned based on interaction with a customer. Waitress never interacted, offered refill or asked if we needed anything. Waitress followed customers to register to see who was giving a tip. I was at the exit, when the manager asked a guest of mine aren't you going to leave a tip??? I looked back to them and said No. We do not plan to return.