People laugh about this because we haven’t seen a big strike in historical times, so their bias is “can’t happen”. But it will. next week, next year, next century, we don’t know when but it will. Actually your actuarial risk of dying from an asteroid or comet strike is close to your risk of dying in a plane crash. It’s small but real.
And, like dying in a plane crash, you don't have to actually be on the asteroid to be killed!