I think the "preserve the environment" is a knee-jerk driven by the same kind of instincts that sell "natural organic food" and stuff - even if we could somehow magically reign in man made climate change there's really no guarantee that the climate will remain stable or that a low probability event like a volcanic eruption won't cause a huge global crisis, etc.
Instead of hoping things remain as they are we should limit our exposure to environment risks.
But to answer your question, because we can't build enough of these to sustain billions of people.
Maybe but then again scaling isn't really the immediate problem - it's building the thing in the first place, replicating should be simpler and by the time it's done who knows what the tech will be.
And while it probably won't work for everyone it will work much more reliably for those that participate in it - not just for climate change but for other catastrophe protection/isolation as well.
What good does convincing people do if the government won't even admit climate change is real?
The "huge" savings for our industry are minimal in the grand scheme of things. It's depressing to realize how we are past the prevention phase of climate change and rapidly passing through chances to more easily mitigate the impacts.
It doesn't have to be for our survivors... We could, and I believe we should, do it for the next civilization to come after ours, even if it's a few alien visitors.
If for no other reason than to leave a legacy of our short existence against the infinity of this universe.
You said it yourself: If you can't mobilize man to fight climate change, you aren't going to mobilize him to prepare for it either.
Why not just assume it's going to become unstable in close future and start building with that assumption ? Large scale isolated citiy domes. Nutrient synthesis that doesn't rely on climate/agriculture. Environment independent energy generation like micro nuclear reactors. Large scale air filtration and temperature control.
As the world becomes more interconnected and developed catastrophic outcomes like super virus/bacteria, large scale nuclear event, etc. become bigger threats to entire world. Why not start building self sufficient and well isolated megacities that can function irregardless of climate change ? It's perfectly possible on 50 year timescale if we don't waste time on shoving our heads in to the ground and hoping everything will stay great if we stop burning stuff.