It's not always about a raid leader "doing call-outs" or "coordinating". It has a lot to do with a raid team discussing strats between pulls... conveying split second decisions to teammates due to the RNG nature of many of the game's mechanics.... and (gasp) fostering a team-like environment that every successful static has.

Your insinuation that only poor players use VOIP as a crutch borders on trolling. And any serious raider would agree with that.