Nicholas Humphrey writes about Questioning Consciousness and concludes with this. Concerning the purpose of consciousness, given that it seems not to be essential to anything we do (according to him), he says:
I think the plain and simple fact is that consciousness—on various levels—makes life more worth living.
We like being phenomenally conscious. We like the world in which we’re phenomenally conscious. We like ourselves for being phenomenally conscious. And the resulting joie de vivre, the enchantment with the world we live in, and the enhanced sense of our own metaphysical importance have, in the course of evolutionary history, turned our lives around.