Can you provide a citation? Because all data points to tipping in no way being connected to the service you provide.
The best way to receive a tip (based on research)? Be female. Be blonde. Have large breasts.
So lets dispense with this nonsense that tipping incentivizes service workers. Its a thinly veiled, widespread (successful) attempt at wage theft.
http://www.tippingresearch.com/most_recent_tipping_papers.ht...
http://freakonomics.com/podcast/should-tipping-be-banned-a-n...
http://www.huffingtonpost.com/2014/10/17/abolish-tipping_n_5...