Why does anyone do anything? Some people obviously just got really into the idea of sailing to the islands. Right now there are people in the world that are super into the idea of going to Mars. There’s no reason why anyone has to do it, but they’re into the idea of it and they’ll find whatever rationale they need to explain the desire.
There are always going to be people whose reason is “because we can”. Going to Mars has, on the scale of a human lifetime, only recently become vaguely feasible. As someone who works in STEM, I’m generally on the side of new technologies unlocking things, though I don’t doubt that population and environmental shifts in the home territory can tip things over from a few crazy dreamers to a more coordinated expansion.