I suspect it’s an unhelpful confluence of several factors:
Obviously people in good situations have an interest(certainly as a pragmatic PR matter; but likely psychologically as well) in the idea that they are where they ought to be/earned it/etc. (And this perception is reinforced by the fact that the successful often do work hard for it; they just don’t see all the people working as hard or harder and getting nothing for their pains).
People generally, successful or not, are not intuitively good at statistics(even statisticians have bad instincts; they just know the math that they ought to use); and the idea that outcomes are substantially impersonal dumb luck is not one that squares well with our socially oriented cognition: people resist the idea that things just happen without any sort of moral logic or agent behind them in all sorts of areas, from economics to evolution to medicine.
There’s also massive survivorship bias: successes tend to be massively more visible than failures(unless they are of the…discrete…school of fortune-building); so while they are the exception rather than the rule their visibility is massively out of proportion with their frequency.
