The point made is, that cell phones are an annoyance that *can be avoided*. The guy breaking loudly behind you, music playing in the venue, etc. are part of the atmosphere. Plus, your opponent doesn't generally stop match play due to such things - but he might if his phone rings.
Plus the aforementioned sneaky coaching bit, ringing someone's phone (which is on vibrate, in their pocket) to alert them that they're making a bad choice.
It's a valid point. I wouldn't mind at all if the rule of the day was "take your phone out of your pocket, turn it off, and set it aside during your match". Everyone's got voice mail on those things. If someone's on call, or needs to be reachable, they can hand their phone over to someone and tell them to answer it if it buzzes and to let the player know if it's an emergency or not.