OK, you all are either missing, or stepping around the reason for the banter in the first place by some players.
Expressive banter is done by players to:
1. Knock you off of your game. If you are listening to them, then you are not going to follow your own play set, and may start to actually listen to them.
2. Try to get information. How valuable would it be if you knew they played Dusknoir? Ambipom? Toxicroak Promo? Mr. Mime? Uxie X? If a player can get that info for free out of an opponent, then they are ready for more situations that may have caught them off guard.
3. To play your game for you, not always correctly. Usually seen in the younger divisions, where an experienced player, especially in trouble, will try to distract a newer player, by telling them what they should do, or are going to do. This we try to crack down on, but there are players it happens to.
4. Make the game fun and enjoyable. Yes, some players actually want to talk and have fun through the game, getting to know their opponent.
Vince