Because it's missing the forest for the trees. Look at total energy usage, across all industries. This is more an indictment of cryptocurrency than it is about actually caring about the environment. Compare it to say, eliminating all gas vehicles for electric cars. Where is the HN thread advocating for that, if the end result would be massively fewer carbon emissions versus this proposal? My criticism is this proposal is like banning plastic straws. It's patting ourselves on the back, with no real solution.