Underclock to save power/heat

For the little what I’ve used Volumio so far, it seems to always be running on full power on my Raspberry Pi. Todays trend is to save power and produce less heat, which is actually important on some new SBCs, like RPI4. So I’m suggesting a feature: underclock when idling on an SBC.
The Rasbian Buster underclocks. Or does it even make a difference?

In Volumio CPU governor is set to “performance” by default, but on my RPI3B+ setting it to “on demand” makes the CPU run some degrees cooler, without affecting performances.
Leaving it to “performance” in these hot summer days caused the thermal protection to kick in and throttle the CPU speed.