Boris Blank only plays synths as far as I know although I suspect he might be classically trained but I've never heard him play anything but synths. On the piece below, it's synths and samples. And his band--Yello--also do this live.
As for folk bands not using synths, that is so untrue that I'm laughing as I type this. My brother's band uses one to imitate a Zydeco accordion because they don't have or know any accordion players. Plus they'd have to hire one every time they wanted to play the song live which is simply out of the question.
I also interjected synthetic thunderstorms with rain as well as a synthetic stream, chirping birds and a dog barking in the distance for another folk band that I helped record some years ago.
Face it, synths are useful as hell and they are here to stay.