In China I very very rarely tipped as my Chinese colleagues advised me that its not required. In Pakistan I tip if service charges are not included. If the service is poor then I still tip but a very minimal amount. The wait staff is usually not paid well and tips are the main source of their income. Especially the waiters who stand on the streets and bring u food and drinks from shops. So a small tip does no one any harm.
Not sure about the practices in Canada though:)