It's way cheaper. Like, it's not even close.

(Note that this IS galvanic isolation--I assume you are talking about transformers, which is the other common way to galvanically isolating circuits.)

You’re right that was lazy of me. But you got what I meant: transformers.

Magnetic isolation more specifically, when you think about it.

So at the same time, magnetically coupled.

Naturally subject to forces including back-EMF which are not shared by optics.

just drive your optics hard enough, you'll see back-EMF

/s

I've driven non-photo resistors to the point you could see the glowing in time to the music ;-)

And smell the smoke.

Now with a 1500W space heater as a dummy load on a 1000W amp, you hear a little music come out of the heating elements without any speakers.