It's because the game is actively hostile towards any type of community building.

- Every piece of non-faceroll content is designed for 8 people only and actively discourages any kind of FC involvement.
- DF means you can be a dick and never suffer any consequences.
- The structure of nearly every boss fight is just one endlessly repeated script where a single mistake is enough to cause a wipe.

In FFXI if you were a dick, you weren't getting any content done. Almost everything could be done with as many or few players as you could muster. Bosses could pull any of their abilities out at any time and even the worst situation could be pulled back from the brink.

Welcome to a clash of humanities natural instincts and design decisions that bring out the worst in people.