A few years ago we bought a house built in the late '70's. All of the original wallpaper was still there (either on the surface or buried under additional layers of wallpaper and paint). When we took it down, what we found underneath was unfinished drywall. It was very rough to the touch, like a low-grit sandpaper, and you could tell that it had never been painted - all original. We had to slick the walls with joint compound to finish them off before we could paint them. The other walls that were only painted were just fine. What I'm trying to explain is not a knockdown or other such wall texture. If you ran your knuckles across this stuff, you'd be sorry.
My question is, what gives? What is this stuff? Is it a normal construction practice to put up a cheaper drywall with no finish coat when you know that you're going to be hanging wallpaper before handing the house over to the original homeowner? A friend recently bought a house built in the early '90's and it turns out he's got the same problem.
Thanks!