Does listening to your favorite song on your bike really give you that extra boost? Sometimes it's hard to stay motivated during a training ride, and the music helps keep you from slacking off. If you care about being in top shape, you think of music as the catalyst to get you there.
Or, maybe you don't care about performance. You just ride for fun or as a means of transportation. It's cheaper than a car and far better for the environment. For you, the music -- or podcasts, audiobooks or whatever you listen to -- is just a way to pass the time. It's fun and enjoyable. It keeps you from getting bored on those long rides.