Well, as to the last point the metal is providing internal rigidity, so that’s why there’s no inner tubing.
But agreed. I cannot see this trumping my replacement costs during my lifetime. It’s cool, and it might be more environment-friendly, but cost/benefit calculation says no.
I haven’t verified the numbers (yet), but the fact remains that no one would drink 3000 ml of coffee a day. And that’s what we see happen with energy drinks all the time (source: I’m one of the toxicologists manning emergency line in our national poison control center).