[iSnow]

But why even have the mobile hangar without a tarp if you want to show off your gear? Just land it and let it sit on the runway for a day or two.

[runjake]

Potential reason: the skin uses Radar-Absorbent Material, which is sensitive to weather and sun. Or they actually have people working on it and they don't want too cook in the sun and aircraft wind/dust/Foreign Object Damage (FOD). Who knows.