I just don't think it being audible is for the attendant as you can't hear them with so many sounds, and you have a screen already that shows everything. For old people seems to be the most obvious, but why would they remove the mute of that is the case. In all reality it's likely some corporate decision, that in their testings made them more money with no mute button vs with mute button. When I worked at a huge national grocery store chain (ahold) it seemed like every decision was made by people who've never worked in a grocery store. So wouldn't surprise me if the reason was some nonsense.