Cause nobody cares about Symphony X anymore. It's the same thing as what happened on the Opeth forum (RIP). The band made such fantastic music as to draw in cultured fans with great, unique tastes. They gathered, they discussed, they argued.
The band then went on to make boring albums, faded into obscurity and long lapses between releases, and forum members started discussing other bands. Or posting joke/non music threads. Over there, it got to the point where it was basically not an Opeth forum anymore. The band shut it down, and rightly so. I'm not going to knock Opeth too much, since they've got a ridiculously awesome back catalog. I'd say up to and including Deliverance/Damnation. Maybe Ghost Reveries.
I can see the same thing happening here, though it might just become a ghost town instead of a haven for 4chan. Symphony X has gone in a new direction, and is slow to release updates, news, or new music. So the fans have resorted to discussing other bands or left for greener pastures.
I stay, not out of any love for SX but for the people who used to make this place awesome, and for UM in a meta-sense which is a hub for good music.