People have been composing and sharing poems since before we had writing. And though there's no way to know for sure (unless someone invents a working time machine), it would not be surprising if it turned out that poetry is as old as language itself.
Because of its great age, then, poetry is an important form of writing to understand--especially if you want to write it. In fact, even if you want to write fiction or non-fiction prose, it can be useful to know something about poetry because it can help make you aware of how you use language and in so doing, it can make you a better writer, whatever you write.
Even if you have no interest in writing, poetry is important because it has been a form of human cultural expression for so long. And, on a purely practical level, understanding how poetry works and how to analyze it will get you though your required schoolwork. The more you understand it (or can fake that you understand it) the more you'll impress your teachers and the better your grades will be.