We need computers for a lot of solid, real life uses.
We don't need cryptocurrencies for almost anything being peddled. They're supposed to be decentralized, but you can't really use them that way in 99% of situations. They're supposed to be currencies and instead they're vehicles for speculation. Etc.
I think their slogan should be: "You don't really need cryptocurrencies for that".
For crypto speculation is <<the market>>.
0: https://hbr.org/2021/05/how-much-energy-does-bitcoin-actuall...
At this point in time, there is no reason to care about this. Maybe we start caring if some insane development happens and BTC suddenly starts representing 10-20% of our energy consumption. Until then, there are bigger problems to worry about.
We already have the technology and the land area.
The ability to tile a land area the size of a smaller American city with relatively bad solar panels to power half a percent of the world's energy usage is pretty amazing.