Constructed is where you go to talk about a deck you want to share or a concept to get feedback on. It's a better format since each deck gets its own thread, and thread derails don't clog up a thread that's 20+ pages long that people attempt to navigate looking for ideas. In constructed, the information you're looking for is right at the top of the page.
The deck list subforum is an outdated waste of space. Sorting by colors makes no sense, because we're past that. People search for concepts.. aggro, midrange, control, ramp, lifegain, combo, mill, etc. If you go to the Temur thread.. what are you looking for? Exactly.. you don't even really have an idea. If you're looking for a mill deck, you know it has to have Tutelage, so.. do you search 20+ pages of every color combo with blue? See what I'm saying.. Deck list subforum is pretty trash now.
When that subforum was created the pool was quite limited to what I'm seeing now. It was elemental enough to where everyone would know where to find specific cards in builds. It was a good place to bounce around builds in the color archetypes as we had just got that ability (2015) of not having basic preconstructed decks to unlock cards for and build upon and could build from scratch.