If there were no cause and purpose to the existence of consciousness then it would make no sense to ask the question, “Why does it exist?”
When speaking about the cause, we must emphasize that nothing can exist without a cause, not even consciousness. This is the truth that implies itself by itself. Nevertheless, since there is nothing else but consciousness that could be its cause, nothing else is left, but to conclude that consciousness itself is its own cause, and to try to reveal and explain this cause i.e. the way it does this.
Knowing that this cause, which is consciousness itself, must be manifested in itself as a part of itself, as a force that makes it exist, which it, as a consequence of itself, cannot resist since otherwise such a force would not have the meaning of the cause.
The purpose of the existence of consciousness must also be its integral and indivisible part and must manifest in it itself. It must always be its aim which it eternally strives to.
Thus the shortest answer to the question why does consciousness exist would be that consciousness exists for it must exist, since it is the force as the cause which makes itself exist. It exists because it carries in itself the aim of its existence which it eternally strives towards, which is the purpose and the meaning of its existence.
It now remains for us, since we are beings built of the same consciousness that the whole universe is built of, to find out in ourselves and explain the cause and purpose of our existence (since consciousness can be cognized only in itself) and thus, at the same time, to reveal and explain the cause and purpose of overall existence.