It's a law there because upskirting is a huge problem. I think OP was referring to an LED indicator so the phone owner/user could tell if the camera is in use by an app though.
Dedicated cameras, whatever their sizes (e.g. gopro), don’t have a mandatory shutter sound. Actual upskirting has little to do with it, phone makers/carriers decided to add the sound to preemptively deflect any issue that could slow the camera adoption when it went live.