It's not... Not every fall/decline is an indication that something bad is about to happen. On the contrary, I think it's a positive thing that fewer newbie investors ^{[most likely]} are buying/selling at the moment ^{[they just come and go (don't pay too much attention to those numbers)]}.
^{- The only thing that should matter, is if the amount of "true BTCitcoiners" goes down drastically [there's no way to accurately measure it (like what @pooya87 said)], as opposed to those that "only" see it as an investment asset!}