I listen to music whenever I can. Like, there are very few times when you'll see me without my iPod. I bring it everywhere and every time my damn headphones break it's like another personal crisis to deal with. One of the main reasons why I listen to music is to prevent boredom, as misskitten said. Whenever I have chores to do, like cleaning the bathroom or walking the dogs, I'll be listening to music. I even listen to it when I work because I clean locker rooms at a gym.
I have a playlist that I use to drive up my heart rate. It's for exercising and needs to be fast-paced. This is also considered my fun playlist, because it has mostly happy, fast songs. It helps me get my "game face" on before practice or games. Then, I have a playlist for sleeping, which is one of the biggest reasons I listen to music. I set the sleep timer on my iPod and listen to music for over an hour every night before bed. Usually it helps me sleep.
Above all, I listen to music because it makes me happy. Anyone who knows me knows that I'm a huge pop music junkie. All those pop artists you hate that are ruining the music industry? I probably love them. If I listened to music to please others, I wouldn't listen to that type of music. But it makes me feel sassy when I sing along to Katy Perry so goddamnit I will.