People do! But you have to sit there and buzz your lips to make a trumpet make sound, but for a guitar you just have to shake the strings. And the sound coming from the amp will do this shaking, completing the feedback loop. So it's mostly portable stringed instruments that get this treatment. There are some violin players that play with feedback effects. I hear Jon Rose is one but I am not familiar with his music. Folks like Jean Luc Ponty and Jerry Goodman make ample use of guitar pedal effects in their violin. And there's a YouTuber out there who plays with them on her harp.
WalterBright|3 days ago