Crypto right now, while being used by under 1% of population use, uses 40% of the energy of the global banking system[1].

In other words, if it were to increase to even 10% of the population using it, it would use over 4x the energy of the global banking system. If that increased to 50%, it would be 20x.

This would be somewhat mitigated in the case of Proof of Stake, but would simultaneously give major players in the market complete control of said market. Y'know, like a government.

1. Research report from Galaxy Digital, a decidedly pro-crypto source, page 8: https://docsend.com/view/adwmdeeyfvqwecj2