Don't know if there is a real "reason" to own them? I don't usually own fish because they serve a purpose, it's an added bonus if they do help the tank, but I normally pick based on appearance and personality.
That said, I first got introduced to loaches with the idea they would keep the substrate clean, and they quickly became my favorite fish! They have great personalities, clowns are a little more shy than say a Yoyo, but they grow larger and have great color.
