I work for a printing company.
Think of this - why everything is printed mostly in black ink? why not navy blue, or dark hunter green?
Because black is a stock color.
The manufacturer stocks it, and uses it left and right.
Most other colors have to be a special order - this comes with increased costs, lead times and paint expiration. If you did not use all of it, paint does expire.
To the printer-happy community let me remind you that painting a jet is not like printing a page where three base inks are used to create a perception of color.
Paint of any color has to be manufactured separately.
So I think that from a manufacturing standpoint it is just so much cheaper to use stock white paint.