Why do some people write haiku?

I say, why not? :)

It's another form of poetry which is essentially just another method of expressing yourself artistically. I personally think a good haiku is harder to write than a traditional poem because the author must convey his message or meaning in only 3 short lines. It's easy to describe the beauty of a sunset in three pages of text but to do it in 3 lines takes a special kind of writer!