In my opinion the reason is simple...all the content that people do is "qued up for". The "Open World" content is not very popular to most people, let's take a look:
1. Hunts...most would consider this a pain in the ass and a near waste of time.
2. Gathering...people get what they need and get out.
3. FATES...only popular in some areas, mainly HInterlands and N.Thanalan still. Dungeons just way better right now.
New Anima Weapon should breathe life back into the open world again...we shall see.