People lose their focus if there is unnecessary hassle going on in TeamSpeak and most of the raid leaders and even regular raiders don't want to be spending their freetime more than necessary on farming SoO for the 47th time. Of course you can do trash talking with trash etc but tbh I don't think no one wants to know how much pussy you got last night in middle of fight where there are tons of shit going on at the same time. It's just a plain fact that people will play better when focused fully and that's what raid leaders want in top guilds, to see your guild do better and not worse when the weeks go by.