The volume in poloniex has been decreased too much, i remember when it was >11,000 ETH but now it is ~1600 ETH, are people collecting (holding) Ethereum to sell in future?
The volume was ~12K BTC at it's highest and now 1.6K BTC.
Some people hold, some trade and some bought to build Dapps.
Normal IMO
it's global i think everyone is searching for more profitable markets to save their money.