I don’t live in a place with particularly high energy prices, but I’ve been reading about countless complaints about home labbers changing to new hardware because of that.
The thing is that, even if the power is cheap a Pi when you’re comparing a PII to a RPi 4 or a modern machine with a “T” CPU if you’ve the money to spend on the new thing you’ll way better, faster CPU, faster RAM, less noise, less power, more modern features, less software issues… at certain point it makes no sense to run that old hardware. Did you ever try to SSH into a Core Duo machine with a Ed25519 key? The CPU doesn’t have the modern crypto extensions making the login unbearably slow, similar happens with other SSL stuff.