Inner liner under door panels?

I have both the front and back upholstered interior panels off, and I didnt find a liner under either of them. On the doors, I didnt find an adhesive either. The rear panels, there was adhesive on the interior metal panel, but not the upholstered panel... leading me to believe that there were liners (if that is what they are called) at some point.

What are those suckers made out of? I think, even if they werent stock, that I will be putting in.