Also, one thing people often overlook - as you settle more places / build more habitats, you are unlocking the vast resources of the Solar System. These might

Also, one thing people often overlook - as you settle more places / build more habitats, you are unlocking the vast resources of the Solar System. These might give you a hand if any single of the settlements (including Earth) get into trouble. This could range from preventing the disaster in the first place (nearby ship deflecting a potential impactor) to helping the survivors (medical supplies being dropped from orbit, habitat with failing life support being evacuated). Self sustaining off-Earth settlements go way beyond just "oops, Earth is gone, at least someone is still left".