To play Devil's Advocate.
The game came back during a time when community servers were being shut down as fast as they popped up.
Do you REALLY think NCSoft would have countenanced such a thing 6-12 weeks after they shut it down?
Can you REALLY blame these people for being paranoid about protecting their efforts?
My understanding of the system is that it was, technically, open to all. But you had to be invited by someone who trusted you. And you couldn't be advertising that you were playing.
Heck, the only reason you're playing NOW is that someone decided to be a buddy-fucker.
And, luckily for you, the environment for this type of thing is MUCH different than it was in 2012-13.