Music can affect you in so many ways. A song can be a trigger for sadness, or it can make you happier. Someone could listen to something sad like So Sick by Ne-Yo to help them get out their emotions. You could listen to Survivor by Destiny's Child to give yourself the motivation to move forward. I like to listen to Hakuna-Matata from The Lion King to cheer myself up. The emotional component of music is something that can be unappreciated. Not all songs trigger emotions in an obvious way, but they all have something in them that that brings it out of you.
In the same way songwriters get emotional when writing, people get emotional listening. A lot of people might think that music is something extra that's not a necessity to people. But music is a tool that creators build for others to use. If you're not good at writing or singing but want a song to show someone you love them, pick one and play it loud outside their house. Apparently, that works for some people.
Music is so good at fueling emotion. Movie directors and music supervisors have to be very specific about what songs they use in the movie. Imagine a drama without a somber piano; or Doctor Who without its action theme song, so you know something crazy is about to happen. It wouldn't be as effective. You wouldn't be on the edge of your seat that way.
Music can even help you calm down, go to sleep, focus, learn, take up time, make you feel less alone, or just help you think of good times. Music isn't just an extra activity people do for fun. For many, it's a necessity for their life and wellbeing. It's a part of who they are and how they identify themselves. Not just for the creators, but for the audience too.