Classical music is very abstract for most people. It is much easier to relate to music that has meaning to your life. Being instrumental music is a big part of that abstraction. I probably would not listen to an completely instrumental concert of most genres unless it was by the absolute best performers. I wouldn't do it regularly. Try imagining any great rock song with the lyrics replaced with a trumpet melody. Still as great?

Classical music is predictable. At most rock concerts you are going to hear new unreleased songs, different versions of songs and some improvisation.

Classical music rhythms and structures are far removed from what has mass appeal. The three minute song with the verse/chorus/verse/bridge structure is what people are used to and, frankly, like. Even artists like Radiohead and Frank Zappa used this structure extensively.

Classical concerts are a passive activity that engage just one sense. People like to go out to dance, mosh, socialize, people watch, etc. Not sit still and be quite. Movies are passive too but they have plot and visuals to engage you. They are also way cheaper.

Personally, most classical music just annoys me. To say that it is one of the greatest forms of art is opinion not fact.