This is a complicated question, but at least one aspect of it is that American culture has always had an incredibly difficult time admitting there is such a thing as social and economic class division and confronting it head on.

At least some of this is probably cultural, it's part of our foundational myth that we broke the rigid class structures of the old world countries and we want to believe that is true. There is of course at least some kernel of truth to it, in some sense, for some kinds of people, historically speaking.

The other reason is that there has been a multi-generational extremely well funded initiative to cultivate media and public opinion against the idea. It's everywhere and is the basis of much of the "culture war" signaling we see around us. Examples include the idea that driving a pickup truck or avoiding lattes is some kind of meaningful class marker, rather than things like who owns and controls the capital of this country.

That effort has been highly effective, in part because it's been well executed and in part because of the total collapse of the concept of a labor party in this country, leaving us with two parties ruled by different professional classes.