Why after all this time there is still no GUI and Poloniex is still a single point of failure?
Jwinterm made a GUI.
The Monero community funded a developer with 14k XMR to develop the "official" GUI
https://forum.getmonero.org/9/work-in-progress/2476/the-official-qt-gui-projectAnd there was that other GUI that was made recently by someone.
If poloniex died, volume would probably move to bittrex.
of course, the real question to ask, is what have you done after all this time to fix these problems?