Some reasons:
1) Some whales are upset, so they sell. The whole PR gag order thing is an example of this.
2) Some BTS Developers (who you would normally expect to be strong hands during downturns), sold for tax purposes, which broke through some support levels and increased the amount of BTS out there among traders.
3) At least of the BTS inflation which is going to delegates is being sold to pay for marketing campaigns, fund development efforts, etc.
4) Some community members got burned in the bter hack, and have withdrawn from buying. For example, personally, I use to make regular small buys every week, but I havent bought any BTS in 4 weeks now, I've been building up BTC instead. If/when I get my BTS out of bter I'll probably feel better about the whole thing and start buying again, probably on a different site.
5) Vesting balances of BTS becoming available from peoples PTS/DNS/etc shares means that soem of these people who had previously locked up BTS shares, but who had become bearish, have been selling them.
6) Most altcoins have been falling behind BTC in the recent rallies, with a few notable exceptions like Darkcoin, Monero, etc which had recent pumps. BTS has dropped in satoshi terms just like most of them.
The marketing efforts and development of features like webwallet, decentralized exchange, etc, seem to be providing some community growth, but not enough yet to overcome these factors. To see BTS go up we need to see either increasing mass adoption, or attract some new whales with plenty of money to spend, or to have some of the above negative factors go away, turning the downtrend around.
The upside is that for those of us that believe in BTS long term, we can get very good prices right now. Close to IPO prices, close to the lows from summer of 2014 before features like assets were even released yet. We can buy BTS now with a full extra year or more of development work, without paying more than the people who bought long ago.