Adding to the previously stated points, regular story threads revolve around a specific event, played by specific people, which happens once, and once been told the thread closes. Meanwhile watering holes revolve around a location and stay as long as the place lasts, and any character who wanders to there can write into it, making these wuite open roleplay threads compared to the regular ones, as been said before me. The nature of these two kind of threads differ so much the watering holes indeed deserved and still deserve their own forum space, at least for practical reasons (separation helps organizing them).