I use to tip in most circumstances hairdressers, taxi's, retsruatants, after poker wins, etc, etc and the only times I didn't was if I felt the service was poor. I have however recently decided that I won't tip if I feel any pressure is being applied for a tip which I have found is a growing trend in the fast few years.
I have particularly found this is happening in a certain casinos, when at the end of a competition I hear a card room manager say "would you like to leave a tip for the valets" or even less subtle the comment of "how much of a tip would you like to leave". I thinks it unfair that people are put into such situations because at the end of the day a tip is a discreationary payment made in appreciation of good service and should not be viewed as expected.
A tip is not something that people should feel they are obliged to make.
I also object too is the growing trend of double tipping. Frequently you are charged a "service charged" on the bill yet you can see the waiter/waitress is viewing up the payment dish to see if any tip has been left. You even now get prompted to leave a tip when you pay by credit card as the machine displays the message "would you like to leave a tip". Double tipping is also happening in poker. You frequently see in some of the bigger comps that they are automatically taking a % from the prize pool and yet we, the players, are still expected/pressured to give a tip if we have any success. I've even seen threads on various forums from casino staff which slate winners who didn't leave a tip. Why do they just start saying "well done sir, allow me to cash in on your good fortune". I even now half expect when I win online a pop-up message asking me if I would like to tip the dealer.

The issue is
no pressure should ever be applied and people should not be made to be embarrassed into thinking they should have to leave a tip. Everybodys circumstances are different, for example sponsored player can afford to tip as they know that their future costs are covered, as can a wealthy business man who mainly plays for fun. But why should a player trying to make poker a living and just developing there bankroll be pressured into making a tip or the recreational player who has been losing for the last 5 years.
Tipping is discreationary and as such should not be expected let alone any pressure being made into obtaining one.