Oddly enough, I still use hand signals, just to keep the practice alive mostly (old school). It also keeps other drivers more aware of your intentions. Having seen other riders do it, there’s little doubt about what their intentions are.
And most drivers just wonder who the hell you’re waving at, I’m sure.
:D
I had to use them in HS driver’s ed.
When I got my first car, I nearly broke my hand by reflexively trying to thrust it out a closed window on a right turn.