I agree, and I don’t know if I’m ready to dive into a full comprehensive interview of the intersections of tipping and politics. However, facially, the whole “waiter needs to earn my tip through good service” is, to me, more of a conservative idea about the importance of hard work and earning what you deserve. A liberal is more likely to think “I need to tip this waiter 20% because they don’t make high wages,” in my experience.

However, I think you hit the nail on the head in doubting that correlation between tipping attitudes and politics. How someone regards serving staff or ride share drivers isn’t a surefire indicator of their politics but just one among many. The Pew article is 8 pages and documents plenty of other factors like the generational divide on tipping (most of my friends are, no surprise, younger than 35, like myself).