Since FSDT created their JFK scenery before T5 was actually finished, they weren't quite sure how the gate numbers were going to be made and where they were going to be. In fact, they weren't sure which gates would be which (which is why they are numbered odds and evens and not just straight through, like the real T5 is) So, they just didn't include them, which makes sense (I'd rather it not be there than have them guess and it be wrong).
They will be added (I assume) in the major overhaul update of JFK later this year.
