We get a variation of this one periodically:
"If you're not a contest, why do you not allow operation on the WARC bands?"
Because "being a contest" isn't the underlying reason events don't operate on those bands. Those bands are smaller than the "classic" bands and thus much more easily overrun during a large operating event. Most contests, QSO parties, sprints, whatever they're called, encourage people to make a lot of contacts in a short period of time. The informal agreement we've all made as stewards of the bands is to avoid WARC+60 for those events.
It doesn't matter if Winter Field Day is a contest or not. We're not going to include those bands. People who don't want to do WFD should have a place to go to avoid the chaos.
"But if you're a real emergency preparedness exercise, shouldn't you allow all bands?"
It's useful to have limitations in an exercise. Even if you ignore the very good reason I stated above, working around constraints makes better operators.
Finally, I want to acknowledge an underlying reason why some people ask us this question. They are preoccupied with "proving" Winter Field Day is actually a contest, and they somehow think the entire WFDA board was born yesterday. We see what you're doing, and it's not changing anyone's mind.