Because we don't have time for it.
While browsing the net, travelling, etc, we can only listen to modern music that is "mentally loud". It oppresses our surroundings, and our thoughts. In this form, classical music doesn't mean anything. It wasn't written to be stronger than the sounds of traffic, or the dialogues of a film.
But nowadays no one has 5 minutes "to waste", to lay back and listen to quiet music that only gives emotions and feelings.