I'm a teacher, I fish to eat!
When I go to a restaurant I assume I will leave a tip because it is customary. That's the main reason. And I accept that it is customary because the prevailing wage in the wait staff industry is notoriously low. But I gage the amount I tip on the quality of the service provided, and I follow what I understand to be the accepted standard of 15-20% for good service. Twice I've left a nickel to make it clear that I hadn't forgotten to tip, but tipped according to what I thought the service was worth when it was especially bad, not just poor.
It is at the sole descrestion of the client to tip or not, for whatever reason they see fit! Period. If i get a guide who doesn't make an effort to put me on fish or has no professional skills I defintly wouldn't tip him/her. happened to me in Hawaii.(long story, Good ending maybe another day) You are the one who decides tip if you will!