I think art of any kind is about the human experience. About conveying it given whatever artistic talent you have been blessed with.
You paint? Then what you paint is a memento of those things you saw and came into contact with during the time period you were here. The feelings you felt, the moments you had.
You rap? Then what you rap is reflective of those experiences you faced during your lifetime. Experiences surely shared by those who listen to and relate to your songs.
You write? Then what you write is representative of who you were and what you went through. What you walked through. What you were a part of.
No art is purposeless, even if its author can find no specific reason for which to produce it. Each piece of art is special in that is a part of a larger collection of artifacts that mark our time here on this earth.
The reason that art in all forms is so popular is because it is a microcosm of a larger truth, larger story, larger experience, larger feeling felt by everyone. One person created it, millions or thousands or hundreds or a dozen people related to it. Understood it. Got inspired by it.
Art is powerful. Don’t underestimate the effect your art is having on others. If even one person gets something from what you create, you are walking in your purpose.