I'm always baffled by the idea that we need to get people living in space for the human race to survive climate chance or other catastrophes. What do you think we could possibly do to the Earth that would make it less habitable than space? Even in the worst, worst case scenario, the Earth's gonna be left with some amount of oxygen-containing atmosphere, arable soil, gravity, and survivable if possibly uncomfortably hot or cold temperatures. Any station we could possibly build to withstand the temperatures and vacuum of space would be much more easily built on Earth.
Long term a big difference would be your space station being isolated from everyone else. This avoids many bad incentives (like prisoners dilemma / tragedy of the commons).
For now, space is just a good training ground. It is not necessary to build isolated eco systems / livable environments on earth and doing so makes no sense financially. Space enthusiasm is a good tool to push R&D.
On an even longer scale it would certainly provide a diverse range of evolutionary benefits, but that would probably go a far bit off topic.
