If you look at the abyss pop items at the AH, they sell like crazy, which proves the AH is a big attraction, the convenience of having the abyss NPC's 3 steps away is almost too convenient. PJ, is just the most convenient complete zone in terms of services vs. distance.

I personally have my HP set in PJ next to the signet NPC, I get a warp scroll, refresh signet (habit), and I have a plethora of options within 50 steps, I can head to the AH, MH, I can even turnaround and zone into Sauromugue Champaign and FOV back to my home nation. Again this is my personal reasoning, considering the clutter around the HP crystal in PJ I assume the same for many others.