Once upon a time, a long time ago, in a world... in a land... there was a zone-specific Looking For Group channel. Then Blizzard saw fit to make it realm-wide so that no matter where you were -- whether questing or gathering or hanging out in big cities -- you could have a channel to make group requests to anyone in your faction not in an instance.
The unintended, though easily foreseen, consequence was that Barrens/Elwynn chat spread to all zones like a plague. And Blizzard took it away, eventually, claiming that it was adding functionality by stuffing it in their new (at the time) LFG functionality. Some protested and created their own LFG channels, but most were satisfied to keep it in the big cities and take it to Tradechat, transforming it forever.