Last time I checked, you can't buy food or pay rent with gold either.

Right? Lots of selling is because people need that passive income to provide for themselves. Goodness, if I needed to, I'd sell the DNET I bagged at 2 cents each if the price reaches 70 cents and I have bills to pay. This is money and back when in University I would've quickly sold anything that made me a few hundred bucks. Why else would you even bother with all of this? I like charts and graphs, but not enough to ignore what the data represents.
Unless you know who is selling on the other end, then you don't know who is selling. It's all just speculation.