IxDA discussion forums - why a linear feed and not categories?

Ever since I started using the IxDA website, I've been curious why the discussions are shown in a linear feed vs a more traditional category or sub-forum organizational structure. I have a terrible time trying to find anything here because the only search tools are keyword based (search box at the top of the page and word cloud on the side) which generally ignore the secondary information heirarchy of time, and thus seem to return extremely old, and generally no longer relevant posts. 

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