Some time ago most NPC vendors and such had "Gossip" text. A bit of flavor text that said a little something before opening up their merchant and/or training windows. It required an extra click before going about your business, and as such NPCs with only one option to select (Show me your wares.. etc.), where made to bypass this gossip entirely.
It was found out however that this text wasn't deleted but simply skipped and could be brought back with a small script.
What does this do?
Simply runs the script "/run ForceGossip = function() return true end" at startup. It forces gossip text to display. Easy peasy.
This doesn't work!
Since gossip text was set to skip by default many new NPCs or those changed by the Cataclysm expansion might simply have no gossip text to say. It's a real shame.