You do realize that proof of work uses a negligible amount of energy compared to banking institutions, right? Its not even worth talking about because its a non-issue.
The real question is: why dont banks just use Monero and get rid of all their wasteful infrastructure?
What? Yes, they looked. And they spread a ton of disinformation that was extremely effective
The fact that this question exists is testament to them.
Its the same for the tobacco industry and the oil industry. They know that they're the big polluters killing people. The looked, and they hired PR companies to spread disinformation.