Because specialized forums such as Legend of Zelda focus on a specific discussion material. The Milk Bar was used for general Zelda discussion apparently far too much, detracting from individually strong threads, and contracting the room for the creation of threads. The Zelda forum was collapsing into itself. It was deemed necessary to close the social threads in select forums suffering from this characteristic. Consequently, people use the forum format to ask questions over the social format and the forum becomes realized. Otherwise it was collapsing back into a single thread format from which it came.
Here's a little history behind the room. The Legend of Zelda room began as a single thread in the Light House, SkylerOcon's "Ocarina of Time Appreciation Thread". That evolved into General Zelda Discussion, the GZD. It kicked ***. We were the most active thread in the Light House, booming with posting. After a while, it became difficult to keep up with some discussion because most ideas get buried beneath the storm of the popular. So we lobbied in Forum Support for a Legend of Zelda room. We had enough supporters that the case went to the Senate and from there, was created as a sub-forum of the Light House by TheBuzzSaw, an ex-Administrator. That was quickly fixed. And so the Legend of Zelda room replaced the defunct Pit Stop (the F-Zero room). SkylerOcon was appointed Moderator of Legend of Zelda for having created the thread that inspired the room, and for already modding Brawl Mario. I was appointed second moderator of the room about a month later. Luigitoilet hopped on a year or so later. And the rest is history.