Because after middle age, people's mood is relatively more calm than before, and they have experienced more things, and gradually they don't like those noisy music.

I am a good example. When I was in my twenties, I liked those pop music, but as I grew older, I felt very bored when I listened to those music again, and even my mood was greatly increased. So I never listened to those pop music again after that, but preferred to listen to some folk songs or some light music.