A couple of years ago I was cycling with someone who came off their bike going down a very steep hill. His helmet did a good job of protecting his head, but he must have landed on the peak because it was forced off the helmet and pushed into his eyebrow cutting it open badly enough to need stitches.
I've had my peak off ever since - though I miss it sometimes, particularly when you get the low winter sun.
It sounds like there's a gap in the market for a helmet with a cloth peak so that you could fold it up out of the way when on the drops and bring it down when needed. If it were made out of cloth it could be pretty big and so do a good job with rain and sun etc.
Neither did mine. If I want a peak I just wear a cycling cap underneath that way I can flip the peak up if I'm on the drops for long or whatever... plus a cap soaks up sweat and holds the rain off better IME.