While the letter was signed by multiple Bitcoin mining companies such as Core Scientific, Argo Blockchain, Foundry Digital, and others, including one of the biggest BTC holders, MicroStrategy, multiple other, more diversified major crypto players have also signed the rebuttal.
However, according to the players in the BTC & crypto industry, the reason why PoS is unsuited as an alternative to Bitcoin’s energy-intensive PoW-based mining process is that it tends to accumulate too much power over the network in fewer hands. Many crypto owners opt to store their coins with large custodians, which inevitably leads to risks and centralization in a PoS system, per the letter.