In order to respond to dynamic lights like on the runway, a texture must use normal maps, and not all textures in the scenery use them.
In addition to that, some objects are made to handle night lighting in a custom and non-standard way, in order to save memory to prevent the sim from loading both the night and day textures at dusk, which would have double the amount of texture memory, causing OOMs and low fps at dusk. The side effect of this approach, is that those objects don't respond to dynamic lighting.
The issue is, the scenery design started almost 2 years ago, when nobody could foresee P3D V4, or dynamic lighting, so the first concern was to save memory and prevent crashes so, improving this would require an extensive rework.
