I think the general idea that everyone is seeing what you are saying has a lot to do with it. The FF crowd is much more cranky and prone to butthurt than most, and people are quick to GM the least little racial/sexist/generally messed up remarks (which pretty much flood Aion's LFG channel, and it's hilarious). I've even been Mordion Gaol'd in XI for an "offensive bazaar comment" (it wasn't directed at anyone). Even though the fact I got Mordion Gaol'd for it was stupid, the GM did give me a nice tidbit of advice: "We really don't care what you go on about between friends, just tone it down a bit in areas that the entire server can see."
When I talk to someone in XI or XIV, it feels more like a direct conversation intended only for those involved, while /say is for those clutch situations (i.e., asking if someone is partying in a particular spot), and /shout is just annoying to talk over with all the Ifrit requests, meld requests, etc.