I think it's because the glass so small & mounted on top of a carbon-fiber looking piece it looks as though the windshield may be tilted away from your eye toward the background. To me it seems spot on with the tail, just a tiny windshield.



The artist may have also used a slightly exaggerated "fisheye" perspective makes the bike appear to curve slightly in relation to the horizon line beyond the background. Lots of concept artists do this, makes it look more dramatic & can fit more of the subject into the composition.