Why not, though?

On a serious note: that's exactly what we're doing with lighters. At least some of them use piezo elements and not the sparkly wheel thingy to ignite the gas. And it's real fun to zap yourself with it.

Wait a minute, what IF

Give buskers the acoustic guitar with a link to the grid and every time they play they’ll generate a ton of electricity (in relative terms…)

Electro-Acoustic guitars use piezos to pick up the audio if you didn’t know

Even if we used piezo, the movement of the hammer would still have to come from some power source, which would still be the same sources like moving steam, water, or wind.

piezoelectricity is just simple electric motor

But not all electricity generation is based on boiling water. Wind, hydro and tidal don't need to generate large amounts of heat to make steam that spins a turbine, they just use natural movement to do so.

All of these are in some way heat engines

Peltier Effect?

Solar thermal power…

Wind is just dry steam

I'm the spirit of this comment, water is just cold steam.

Excuse my blatant ignorance, but what is aeolic energy? I've never heard about it before.