A.O. Scott considers that question in The New York Times. I am not sure I can sum up his view in a sentence, so I don’t know if this is criticizing him or partially agreeing with him. In any case, I don’t see growing income inequality as the main driving force behind the decline of middlebrow American culture. An individual’s level of education often predicts cultural consumption better than does his or her income, and education has not in general declined in this country.
Furthermore many forms of culture have grown much cheaper. Once you are paying for cable, the marginal dollar cost of watching a show or a movie at home is zero. Songs and music are much cheaper than twenty years ago, and eBooks make many (not all) books cheaper. In other words, if stagnant income groups wanted middlebrow culture, they still could afford it.
Global markets are growing and those markets are often relatively middlebrow in their orientation, which should maintain the return to producing middlebrow culture. And the United States continues to grow in population, even though the middle is shrinking in percentage terms. The supply of creative activity is quite elastic, so it is hard to argue the wealthy have placed all relevant artists in their employ and thus choked or starved the middle.
It is much more expensive to organize a middlebrow art exhibit than fifteen years ago, and we see fewer good ones, but that is mainly because of 9/11 and insurance rates and related institutional issues, not income inequality.
My view is a lot of people never wanted middlebrow culture in the first place, at least not in every sphere of their cultural consumption. The internet gave them more choice, they took it, and much of middlebrow culture lost its support base. Consider one area where the internet still doesn’t play that much of a role and that is theatrical productions. You can watch plenty of theatre on YouTube, but it’s not such a close substitute to seeing the show live. And if you look at Broadway theatre, it seems more relentlessly and aggressively middlebrow than ever before. Ugh, that is why I stopped going. NFL football seems middlebrow to me and the audience base still is there, again because the internet has not come up with a close competitor. If the sport has a problem it is the violence and injury, not that we’ve evolved into a mix of polo ponies and roller derby.