The future is uncertain.
Just because things can get better, doesn't mean they'll get better in our lifetimes.
Which means we need something more durable than narrow, short term self-interest.
Acting honourably requires us to accept the constraints of a value system, despite the catastrophic risk this entails.
From a rational perspective, this makes no sense. But maybe that's the point.
Reality is cutthroat.
Without putting our lives on the line, we will not survive.