How about rockwool? It seems like it has a lot of advantages: soundproofing, termite resistance, hydrophobic, fire resistance, recycled content, inexpensive. What am I missing?
Rockwool is excellent. It's not an air or moisture barrier on its own, but combined with spray foam, it's best of both worlds. They call it "flash and batt" and it's an approach that's more and more widely adopted.