Tipping....

I am glad to give tips where tips are due. Example: the other night, DH and DS and I went to eat. at a local family resturant. Our waitress was very polite, got the food out on time, got the drinks and anyother things we needed or asked for. We were glad to leave a $4.83 tip on a $20.17 bill. On the other hand, a few days ago at lunch (a a buffet style resturant), the waitress only came to check on our table one time, never re-filled our tea, never siad thank you. Did she deserve a tip?