We have to at least try to get into space, because over time Earth will become inhospitable to life again. We're in an interglacial period, but the glacial periods are more prevalent and last longer. And unlike planet-wide asteroid damage of the dino-killing Chicxulub impact 66 million years ago, interglacial periods only last thousands of years. That's well within the span of homo sapiens' possible existence. We really need to start planning for the next one. We could use the option or at least the technology.