Personnaly I do it because it is fun to do. It also test my knowledge of a language and allow me to improve on this language.

However, I avoid to do those kind of thing for professional code and always favor readable and easily understable code.

Codewars is not real life project guys, it is fun to have those kind of solution upvoted, it show of what a language can do and help reader to improve, even if it should not be applied in a professional context !