Most suspicious in my mind is the core presupposition (not a contention, a presupposition--the article doesn't even argue for it!) that rich people will step up to the opportunity to fulfill their noble obligation to give more to the less wealthy. Having known some pretty stingy wealthy people (and some very generous blue-collar people), it's not obvious to me that this is true.
My experience was that wealth doesn't seem to matter much for tipping. When I first started I always hoped for the order to the big houses, but as I gained experience I realized it really doesn't matter. Some wealthy people gave generously, as did many poorer people. One of my favorite customers was an illegal immigrant living in a trailer park. Every time I delivered it was a $5 tip (which in those days was a great tip). On a side note, when an order for this guy came up I always made sure the cooks did a great job, and I took his order first.
They have no idea about money. It's a banana, how much could it cost, ten dollars? They just have no idea. None. I couldn't even have gotten mad if they didn't tip or gave a shitty tip, young man yells at sky.
Then you could deliver to the same house and someone else answers and it's the person that started the business that paid for the house, and they will tip. Because they know how to motivate workers, and that's money. In my ancient pizza delivering days 2 dollars was a good tip, 3 dollars meant the next time I'm out on a run with three stops, yours is the first. If you don't tip, Greg gets your order. Greg's the kid that only got hired because his dad is friends with the owner, and he tends to get lost and we have to send someone out to rescue him.
Money makes the world go around.
What kind of credit card they have. How they decide what to order. Their mannerisms.
Even the most low-key wealthy people act differently than poor people. Spend enough time around both and you can tell, even if they're dressed identical.
I know that in my own case there was a period in grad school where it was only slightly below 50%, implying that almost 10% of my wages were spent on tips... what exactly are the "best" tip percentages that service industry people leave like?