1. I don't want my children to die. And i don't want all the life on earth to be eliminated by a random asteroid.
2. Imagine two planets, people on one of them believe that expanding is the moral imperative, and the other want stay where they are. Eventually the people from the first planet will be technologically as far away from the people on first planet, as we are from people on Sentinel island. And therefore will be completely reliant on goodwill first people.
3. The only way to preserve life on earth is to develop space technology, once we have sufficient industry in space, controlling whether on earth will be a simple task, trivially solving climate change issue.
