Because singers of this day and age are typically harder to understand, the visuals help to tell the story the lyricist wanted to tell in the writing of the piece. It makes the song easier to understand and enjoy, and by bringing more appeal and getting people excited about the videos for this reason, it spreads the music to a wider range and makes the industry more profitable to maintain. These are most of the pros, those and it gives more room for creativity and connection between the film and music industries. There are cons though: making a single music video can get expensive depending on how creative you get with it. You have to have connections and equipment and a lot of other things including storyboards and actors and most likely green screen capabilities and it can often be hard to diversify the styles of your videos so that you can keep your viewers coming. This comes from raw experience ;) if you have any questions let me know
