Lodge used to grind the insides smooth before seasoning them. Several years ago they stopped doing that. If you get a pan from before and after the change, you can really see the difference. It’s not the usage that made them that smooth.
Some people take their new cast iron stuff to a machine shop and have them grind it smooth. It can probably be done at home if you have the right tools, but be aware that it’s a very messy job! Wear a dust mask and goggles.
The rough surface is normal with the casting process. The only thing I’ve ever cast was a ring in one of my art classes, but the surface came out with that same texture. Took me days to smooth it out enough to polish.
Well, then I guess my lodges won’t get as smooth as Granny’s skillet then. Hers is still my favorite. Although I just bought a lidvd that has those lines in it, so you can grill stuff and have it look like you did it on a barbecue.
I suppose they quit grinding to save one step, to make them cheaper.