All boards and child boards on the forum are important and serve their own purpose. In my estimation, they help to keep the forum well structured and very organized. I know you may soon ask about the archival board so let me answer it to the best of my knowledge. Just like the off-topic board, the archival board is equally important, it's almost like a personal draft book for some users or a scratchbook. They put their thoughts, if it makes sense they proceed to posting it, if it doesn't they move it there if they don't want to delete it. Also the mods move stuff there too that doesn't fit in off-topic or other boards.