To be fair, there are a ton of different types of casing out there, and some artificial casing is easier to consume than the natural stuff.

But, yeah, you have your paper type casing, which may or may not be edible. You have plastic casing, not edible. But there is collegen casing, which is pretty much an edible plastic. and then you have the natural casing, ie, animal guts.

Source - worked for a place that supplied butchers and meat processors.