When you're discussing space exploration, and more specifically space colonization you're never speaking in your or even your great x5 grandchildren's lifetimes. You're speaking at the time scale of civilizations, where something like an asteroid is a very real concern. We're not guaranteed to know that one is coming and "build a bigger bunker" is not necessarily a panacea, especially if the surface is completely decimated. Having a few thousand people in a bunker in that scenario just makes it a bigger coffin.

And exploring Mars isn't about protecting the people on Earth from an asteroid. It's about having multiple civilizations so that when one of them eventually gets wiped out by an asteroid (because at these time scales it is an eventuality, not some super-unlikely thing), there are others and the human race can survive.

Literacy or hunger are not scientific problems, they're political ones.