Auto interiors

I've noticed that the interiors are not often sketched out. The windows are often blackened or somehow shaded to obscure the interior. What are the primary reasons for this? Are the interiors just not important style-wise or are they just too difficult to draw?

FOr me its just a perspective problem. I dont get the whole "perspective" thing so I freehand everything, and interiors usually end up looking like their on an escalator goin downstairs or something, lol

I just think they ruin the style if you have a cool car with windows not tinted! It just doesn't work for me...