Energy is so cheap it's not really worth the effort (economically).

And if it would be more expensive stuff like cooking or washing clothes would still hurt more than downloading a file with a big PC.

It is cheap until it is not. Cost of energy is dependent on where in the world you live, how it is sourced, time of the year, and if there is a natural disaster. Some places in the world, like parts of rural India, only have access to solar.

Expect energy cost to also go up in the USA with the administration pushing to phase out renewable energy with fossil fuels. Fossil fuel never goes down in value. They may seem to go up and down but over time always increase.

As we keep adding more and more computers to the grid it will require more and more energy.

Second hand computers with this energy efficiency will benefit the poor and counties where energy is still a costly commodity. I don't mind paying the initial cost.

Energy is cheap in some places of the world. Something that saves me, say, 50Wh, nets me 150€ at the end of a year. "Don't make things more optimised because my electricity is cheap" would keep us all stuck with big energy bills.

> I definitely value lower power usage when idle. My desktop PC uses ~150W when idle.

These two statements appear to be in conflict. 150W is a high idle power consumption for a modern PC. Unless you have something like an internal RAID or have reached for the bottom of the barrel when choosing a power supply, 40W is on the high side for idle power consumption and many exist that will actually do ~10W.

There's a couple dozen of us stuck with older hardware because we have less money to throw around.

In this context "modern PC" is pretty much anything since approximately Ivy Bridge. You can get one of those -- the entire machine -- for less than $50, and somewhat newer ones for around $100. If you're currently using something with a 150W idle power consumption on a regular basis, you're losing more than that in electricity.