I think it's part of what I've seen called the "temporarily embarrassed millionaire" effect. There's a certain group of poor folk who have been convinced that, any day now, they're going to come into wealth (through some nebulous means and no real action of their own), and so act like they are already part of the wealthy class. Even going so far as voting for benefits for the wealthy and against their own interests, including voting for the destruction of the very social programs that support them.

Just an assumption on my part, but I think you would find a correlation between political affiliation and treatment of service industry staff when it comes to lower income people.

There's a world of difference in disposition between new money and old money, in my experience, and flashy-car-and-expensive-jewelry rich is decidedly new money. Families with generational wealth tend to be more discreet about it, and often have a "noblesse obligee" mentally about how they engage with the world. New money's much more likely to pull the "don't you know who I am?!" card.

Similarly, there's a split between working class folks who know the score and recognize that they're all in it together with the guy behind the counter, and the sort of temporarily-embarrassed millionaires who have themselves convinced they're better than they are.