For the tapping, it's said in the tech manual that the tapping of panels or commbadges is largely habit. The one time it's most egregious is in the first-season finale when Riker is paged by Picard and walks halfway across the room to tap the comm panel on the wall, just so the writer could have the obnoxious cryo-refugee see and be able to figure out how to call the bridge later. Aboard ship or for intrafacility comms, just speaking to the air is all you need. When you're outside and receiving on your commbadge, you just need to speak in acknowledgment. When you're inside and receiving an outside transmission, you need to go to the commpanel (since it's usually a video feed). The only times you need to tap your commbadge are when you're outside initiating a call, or to end it (or put on hold), rather than saying "[surname] out".
Would've been nice if they'd been consistent with that...
--Jonah