Here's one example why we should care: in 1977, diving in the human occupied vehicle Alvin, scientists investigating a volcanic ridge 2500 m (1.5 miles) below sea-level found something totally unexpected -- lush ecosystems thriving at hydrothermal vents fueled by chemical energy released from the Earth's interior.
There was also a widely shared view that so long as any nation on earth retained the capability to manufacture chemical weapons this sort of residual deterrent stockpile would be required.