Isra, please, though I agree that you must tip to maximize fun and minimize irritations, you must get it through your head that you are not in a regular normal run of the mill city if Mexico.
Drug Violence aside, if you go to a city like Guadalajara or Mexico City or one of the state capitals of the country, you will not be hassel by service providers of any kind seeking tips.
(Beach and other tourist points not included cause in some cases any one is hassled for a tip there)
It just the other way around, you are visiting a part of the dark side of Mexico that demands tips cause they are paid zero by the owners of clubs, hotels and bars.
And I dare say, even in your own US of A a customer is hassled by anyone that offers a personal service and demands a tip (hair groomers, pet keepers, waiters demanding 20% tip), people that we never ever consider here in Mexico tipping as high as you do in your country
And beware if you don't tip them, cause no one knows what will happen to you when if you return for your services.
So guys, stop complaining, cause people asking for tips will not go away ever at TJ.
If you don't like it, stay home.