We need to live in space because having all human life on one planet is intrinsically unreliable. However lucky we get, every year there is a tiny chance that

We need to live in space because having all human life on one planet is intrinsically unreliable. However lucky we get, every year there is a tiny chance that we are all killed by anything from an asteroid impact to global climate change. No matter how small that chance is, what it means is given enough time, eventually this planet will no longer be host to humans. We need to branch out to other planets before that happens if our civilization is to survive. Yes, it requires a lot of effort to do it. It required a lot of effort to build the first airplanes (I can find you many, many quotes similar to yours about how 'man was not meant to fly though the air like a bird'). That doesn't mean you shouldn't try to do it. I will also remind you that at many points in history (for the vast majority of its existence in fact) the Earth was an inhospitable wasteland. Given time and innovation we can make space a more welcoming environment.