Because he can...and there is bigger nonsense than this floating around here. Where shall I begin? Take anyone of Alpha Males post for example...
Ducati is going to do something along those lines, no matter how much wind tunnel time it takes, Audi has deep pockets and mad resources. That is why they left the wings on for testing.
they left the wings on for testing so they can have a baseline to compare the 2016 bike vs 2017 bike. the announcers even said it during the tests.
A plausible excuse, but smoke and mirrors I say.