Let's say you have cancer, but you're also in the middle of a famine and can't feed yourself. That's a more fundamental problem, right? Zoom out, what good is curing cancer in the face of apocalyptic climate change?

The case for Mars is that “humanity putting all of their eggs in one basket” (Earth) is the most fundamental problem of all. Everything else is a band-aid.

(Cancer can’t be cured, incidentally: https://tapas.io/episode/58081)