I don’t think it is proper and have noticed this going on more and more. The last time I went to a restaurant with some friends, the waiter kept coming by and sitting down to chat for a few minutes. This went on through the whole meal. We were celebrating a birthday, chatting with each other because we hadn’t seen each other in a while and really didn’t welcome the intrusion. We were polite, but not really friendly. He didn’t get the hint.