For all you know Dream Market is right now "scrubbing" a bunch of BTC by suppressing the price and accumulating Monero for a big announcement coming soon! If it were me, and I was as crooked as these people... it would be a no brainer after watching the last rise to an ATH.
Edit: In fact I would be surprised if there weren't a lot of others doing the same thing!
True, probably more of these markets will jump on the same waggon and implement XMR, could happen close to the GUI announcement as this would enable the average Joe to use it and push the price continiously up.