a) Apps run on touchscreens. Your hands cover the screen so sometimes there is no visual cue. b) When an app is slow to respond, the audible cue lets you know

a) Apps run on touchscreens. Your hands cover the screen so sometimes there is no visual cue. b) When an app is slow to respond, the audible cue lets you know that the action was performed c) iOS and android devices usually do 1 thing at a time, so you know the tap sound could only come from the current app. Imagine what it would sound like if a bell rang every time a web page in your tabs was updated. You 'd still need a visual aid to tell where it came from d) because apps lack in content and try to make up with visual effects and sounds