I can stand a lot of things, but one big peeve of mine is a missing headliner on anything. That one thing would stop me from purchasing any vehicle, but that's just me. That car looks that good but you can't replace the headliner? Come on...
Agree, IMO the seller is letting his car down by not replacing the headliner. Rest of the car looks too good to be put up for sale like this.
Probably the same thing that happened to every other headliner built like that. The adhesive started to fail and the fabric fell down. It looks like instead of repairing it he just took the headliner out completely. Now the new owner will have to find a new headliner board, upholster it, and install it and hope there aren't any missing clips, screws, fasteners, etc. He would have been better off just pulling the fabric off and leaving the ugliness of the foam behind. Good luck finding and then transporting a headliner for that thing without damaging it.
If I had to guess, I'd say the chances of you having a perfect, original headliner in a GM box wagon are about zero. They have pretty much ALL failed by now. Mine was toast when I bought the wagon, so it was the first thing done.