Mexico is Mexico. It is not the US or Canada or Australia or Egypt or any of the many other countries mentioned. Many servers in Mexico work for tips and only tips. And we do tip based on the level of service we receive - which in Mexico - at least places we go - has be excellent so we tip accordingly.
A story - - My Aunt lived in San Miguel de Allende for many years starting in the mid 50s. I first went there in 1971. My Aunt had a maid who came in every day and worked for 8 hours - 6 days a week. The wage at that time was $5 per week. I was shocked. I asked my Aunt why she did not pay more. She told me that this is what the Mexicans pay their help and if people from the US come to Mexico and pay more money then the people will want to only work for US wages and the Mexicans will not be able to hire help. The maid had 5 kids and her husband had gone to the US to find work. She was on her own with 5 kids. Each day my Aunt would give her money to go shopping for whatever my Aunt put on her shopping list. My aunt knew the maid would go find good deals on the items and negotiate the best price. She also knew the maid would keep a little of the savings for herself. Since my Aunt knew this she figured it was sort of a little tip. I still did not think this system was the best and too this day I wonder how that maid survived on that amount of money. But as my Aunt explained - this is the system in Mexico. Today we go to San Miguel and see all the rich people from the US building mansions on the hills and throwing money around. The population of San Miguel has grown as more Mexicans move there to try to find the good paying jobs. San Miguel has changed a lot over the years - as have many other parts of Mexico.
With all that said we still tip according to the service we receive. We also do understand what things cost in Mexico and how to find the bargains - as the locals do. If our tipping brings up their standard of living a bit then maybe it is a good thing. The Mexican economy is growing as more industry of all kinds locates there and better paying jobs can be found. As more Mexicans enter the middle class they can spend more money. Some of their money is spent on goods produced in the US - as well as other parts of the world. Workers are consumers and if consumers have more money they buy more stuff which is good for all economies. Spreading a little money around can help everyone in all economies.