It's a really cool idea. I also see a potential benefit to preventing acoustic keyboard eavesdropping. I've seen some newish streamers not show their screen when doing something sensitive like logging in somewhere, but you can still hear their keyboard.

On a slightly related note, I quite like listening to mechanical keyboard sounds when my favorite programmers are doing a stream. I ended up buying one for myself because I just had to hear the sound up close. Mmm...