The Purpose of Shiva is Companionship i.e. Love.

It is a misconception that Shiva destroys the Universe for Shiva and the Universe are one and the same. That being said; Shiva is in constant flux for constant companionship. It is not good to be alone. The purpose of Shiva companionship more commonly known as love. The above remains an abstractions of sorts but it leads to absolute truth.
~ Wald Wassermann, Physicist