This is largely an American problem, although it is spreading due to global media.

I blame it largely on Calvinism and the prosperity gospel:

"Good things come to good people" -> "If good things didn't come to you, you're not a good person" -> "Poor people are poor because they are bad people, and we should not help them" -> "It's okay to help billionaires, they wouldn't be rich if they weren't good people"

A lot of poor people have this view in the US, which you would think would make them reconsider it, but they solve this with mental gymnastics: They and their in-group are good people, so obviously it's okay to help them and the good things are coming any second. Another reason not to tax rich people, they'll be one soon!