We get to experience the Brand New again. We get to learn things that are unlearnable right now. We get to leave behind a planet whose ecosystem has been screwed by its current population and try to make the right choices on a new one.
But mostly?
Because it's hard, and rising to the challenge can supersede politics and superstition and, we can only hope, recapture the sense of, "holy shit, we did it!" not experienced by a large percentage of our population since 1969.
So what? Does it improve the human experience more than addressing human biology & cognition?
> We get to leave behind a planet whose ecosystem has been screwed by its current population and try to make the right choices on a new one.
Unless you can substantiate that claim, I don't necessarily agree. You are also speculating that we would somehow make better choices with a different planet than this one. Not that it's impossible, but I find it hard to believe. Are you saying that it is more practical to terraform a planet that doesn't support life than to address existing environmental issues on Earth?
> Because it's hard[...]
That's not a very good reason to do anything. It might give people motivation to do things, but "because it's hard" speaks nothing to what we stand to benefit from doing said thing. There are plenty of things that are hard to do, like building a giant pogo stick that can bounce you into outer space, but that doesn't necessarily mean it's worth the time and money to do.
But mostly?
Because it's hard, and rising to the challenge can supersede politics and superstition and, we can only hope, recapture the sense of, "holy shit, we did it!" not experienced by a large percentage of our population since 1969.