I use them because I don't want to miss an targets. I would guarantee if I wasn't then I would miss targets so it's a simple choice for me.
Also the external noise can attract unwanted attention from walkers, cyclists and other people you don't want knowing you are detecting. I don't mind a quick chat with anyone, but when you're surrounded by 6 pikeys who've heard your detector from 200 yards away that's a different matter! also from another aspect if you are close to farm dwellings, I don't think Mr Farmer is going to be happy listening to bleeps all day, because the noise does carry an awful long way!
Probes are a lot quieter and most can be made silent and use vibrate only, or you can muffle the noise with your hand.
So go ahead, if you don't want to use them on your own sites that's fine. But don't complain when someone else comes on and cleans up and they're using headphones