There just aren't enough players to justify this right now, and the in-game interface for raids is really confusing and useless. People show up in invite and you have no idea (well, i do now) if that means they're in the area, online, or whatever, typing things in chat usually means nobody will see it, etc.
The result is group content is insanely hard to do. Pretty much limited to people who hang out in IRC, and even then the movement restriction regularly keeps people from being able to do raids.
I'm leveling an alt to group with myself for the first slime raid with my level 40 character because attempting to do it with people that actually need it would be pointless and nearly impossible. This is a problem.