You're asking for the meaning of life there. For some it's pure unadulterated hedonism, for others it's religion, for others it's science or technology, for oth

You're asking for the meaning of life there. For some it's pure unadulterated hedonism, for others it's religion, for others it's science or technology, for others it's their children, and so forth and so on. But for many the continuation of our species, whether or not we're a part of it, is certainly quite a crucial part of it. As an aside from this, you also don't know your statement to be true. Our planet has, multiple times, killed just about every single living species on it. We'd probably stand a decent chance of partial survival due to technology and intelligence, but on the other hand we might not. Think of all the [relatively] near miss large asteroids that we detect only long after it would have been much too late to do anything. And that's something we can actually control. An unfortunate gamma ray burst or other form of harmful electromagnetic radiation could be GG earth with little to no warning or even chance to react. The chance of an extinction level event happening at any given point is very low of course, but they have happened and will continue to happen. It's just like winning a lottery, one that you'd very much prefer not to win.