JFK is not the easiest place to take an A380. IIRC there are only 4 A380 compatible stands on the airfield at T4 and for T8 only one entrance and exit to the ramp area and even that has a restriction on which direction you can turn. The 380 is limited on which taxiways it can use too.

That on top of the cabin product and capacity/frequency/schedule adjustments previously mentioned mean it just wouldn't happen given the current infrastructure.