This, because we have no other choice, we had no choice otherwise. The fact is the state of existence has no point of choice, no past or future, just a state of presence in one form or the other, like states of matter. We may live through many years in time, but we just exist, as if a moment out of time, just like a ripple, slightly raised from the rest of the ocean and traversing along the direction time flows. We sense the passing of time because we are not completely immersed in it.
This is really as basic as one could get. The questions about life are easy to contemplate, but questions about existence are always impossible to circumvent for an answer. We could say human life is an instance of an existential nightmare, where nothing really makes a very good sense. The questions about existence are the domain of metaphysics, transcendental philosophy, spiritualism and mysticism.