Heavensturn-Why no Chocobo Hat?

[Lukahn]

Because there is no year of the chocobo. 2014 is the year of the horse. The other kabutos are from the old events 2011-2012 except the snake kabuto, because the 2013 new year event was dropped (server shutdown).

In 1.0 you got the chocobo hat from the chocobo caravan achievement (which don't exist in ARR sadly).
Maybe SE bring later a new chocobo content with the chocobo hat as a reward.

That explains it, though the artwork for the holiday is a bit decieving, since there is a chocobo hat in it.