Imagine a scenario where the human race is moving towards extinction due to a downward spiral into the genetic abyss. The apocalypse is near! If the projections are extinction, what choice would people have?
The number of potential scenarios is boundless. Only limited by one's imagination. Potential scenarios: an asteroid strike, a virus, the Sun going nova, even another species of animal supplanting humans. I have even read a story where the Earth was dying of "old" age.