But how many people actually pick the Magic Flute when they're in the mood to listen to music? It's just not that popular.
And when most seats at a classic music concert are ~$100 or more, with only a few rows in the ~$50 range, I'm 100% sure that skews rich. A night out for the family will be hundreds of dollars. It's not a $15 movie ticket.
Here's tonight at the New York Philharmonic:
In fact classical consistently appeals to older listeners. The median age at most concerts will be the far side of 50.
For a certain kind of music lover, pop starts to sound boring and samey after a few decades. Classical scratches that itch.
Orchestras and opera companies regularly worry about this, but in fact the supply of new listeners tends to be fairly stable.
The biggest marketing change was the extra push given to classical from around the 1920s to the 1970s. There was huge state and network support for classical music, and a lot of effort went into bringing both live and radio performances to US audiences - partly for noble reasons, partly so agents and networks could make money by marketing the work of performers and conductors.
From the 1970s the nature of funding changed. Sponsorship became corporate, and then the corporates cut it because they got a better return from sport and straight advertising. So a lot of the old support disappeared in the late 80s and 90s. The orchestras and opera houses that survived are more or less stable now, but it's a smaller market niche than it used to be.
Classical music isn't "popular" just like classic literature. Pride and Prejudice won't be on the NYT Best Sellers anymore than a new Beethoven Piano Sonata recording would top the Billboard Top40.