I think there are a lot of reasons. One of it is that we don't teach children to listen to it. Sad fact is that our children are already the second, maybe even the third generation that doesn't grow up with it. Radio stations play what people want to hear. Because a lot of people barely know classical (b.t.w. it is in fact a wrong word. Classical music is music from the Mozart Era only) they don't ask for it.
Most classical music requires you to listen active and be quiet while you listen. At least until you a peace that good that you can do other things while listening to it. That makes it less good as background music while you work
There is hope though. As a conductor, I give a lot of concerts with a chamber orchestra.(ensemble) Heavily (Or Heavenly) inspired by the way Leonard Bernstein did it, I go to schools with 10 to 15 musicians.
Most children, in age varying from 4 to abut 15 years actually do admit that they liked the concerts, more than then they thought. It requires that we, as musicians try to build a bridge. Not by saying "Our music is the best", "This is true culture and your music is rubbish"
First of all, it isn't. There's a lot of classical music that had exact the same purpose as popmusic now. Entertainment!
Not every single piece of Classical music is better then Rap, Hip Hop or other Pop(ular) music. It has a total different meaning. I may like it or not. Just as other may like classical music or not.
The fact is they can 'live peacefully together'
If we give young people the feeling that their music is Rubbish, trash etc. They will never start listening classical music.
Filmmusic builds huge bridges here.
Listen to Starwars filmmusic, then to the Planets
Listen to Lord of the Rings, then to a small part of Wagners Ring.
Creating associations does miracles. Just complaining doesn't. Only we can change the situation!!
Edward