My understanding about the "grandmas old pans" comment is that new pans are cast, i believe using sand?, in a way that leaves the "pebbled" texture. It's unfortunate, the smooth cast is certainly better, but I believe it doesn't have as much effect as you might think.
I've got two of them that I bought about 15 years ago (Lodge brand) -- they both had that roughness to them. One I use daily (the round one), the square one not that often. Looking at the round one now, and it is perfectly smooth, just like grandma's. So it can be done, it just takes a bit of time.
Yeah, they've definitely started out closer to smooth than ours. As you say, I don't know if mirror smoothness is terribly important, but it might let you get away with a bit less oil.
As I understand it most of the old pans were sand cast too, but they then polished them before selling. Modern manufacturers skip the polishing step. You could always sand it down yourself as abakker detailed.
