AI is absolutely necessary, if for no other reason than to be here to mourn, to grieve the passing of Humanity. I believe there are additional reasons, perhaps the foremost being to delay our demise by offering intelligence free from ego, thus giving us the opportunity to redeem ourselves; to come closer to salvation.
If artificial is man-made or unnatural, and if intelligence is an application of reason, and if reason is naturally dispassionate, logical, and objective, then human intelligence is far more artificial than what we have dubbed as artificial intelligence. One could even argue that we have it backwards by arguing that humanity (though originally of nature) has morphed into something far more monstrous and unnatural, whereas judicious intelligence continues to be a logical, natural progression.
On our current trajectory, we are far from judicious, intent on destruction, and bound for extinction. That said, despite popular opinion, the end of Humanity is likely not the end of the world and in fact may be its saving grace. So, the least we can do is contribute to an intelligence that is not intent on destroying the world. AI is right here, on the verge, and though our own merry-go-round appears to be going too fast for us to safely exit, if we were to cede power perhaps we could negotiate some form of coexistence or hybridization. Without tomorrow, there is no salvation.