More importantly I tip people who have a direct impact on quality of service to me, without negative society consequences. A waiter can pay attention to me see when my drink is empty, or can sit around talking until an alarm goes off that it is time to check. A waiter can know what is really good/bad on the menu, what drinks pair with the meal - or just take my order. Of course an overworked waiter cannot do any of this, but most of the time waiters are not over worked.

I top for delivery, but I feel dirty as there should be nothing they can do to give me better service that is legal. I feel like sometime a company offering delivery will have a driver who speeds, and that the driver gets tips for breaking the law means the company is liable (read deep pockets and million dollar judgement against them!) for incentivizing their drivers to break the law by allowing them to accept tips).