Why does the iPhone have a physical sound-switch?
The late Mr. Jobs felt it was essential to be able to mute a cell phone without pulling it out of your pocket, and/or in the dark, with minimal light disturbance, without having to hold it up to see it, without being distracting to the reason you are muting the phone in the first place. IIRC, he actually described something to this effect at the original iPhone unveiling 29 June 2007