1. We equate a quiet shutter with a piece of quality equipment. Of course, there are plenty of not so great cameras with quiet shutters -- and digital point and shoot cameras, anathema to many of us, are silent if you shut off the fake shutter sound and the focus chime. And, you can't call a Canon T90 quiet, though it's a superb camera.
2. We think a louder shutter disturbs subjects. What that really means is, you can only get one shot, since the shutter noise calls attention to you. But let's be honest, it's rare that there's not enough ambient noise to mask the shutter sound, and how many of us have actually heard the shutter noise from the distance of a subject? Remember, we're hearing it from several inches away, so it sounds a lot louder than it really is.
3. What disturbs subjects more than the sound of a shutter is seeing someone with their camera to their eye, pointing in their direction. If stealth is really needed, this is the more important consideration.
