How couldn't they know how to smoke things? I fear this is one of the isekai where the local hairy barbarians don't know even the things that have been around since the ancient Egyptians, and so it's up to the sagacious Japanese man to teach them the very basics of life. I wish LN authors/mangaka did at least a little bit of research. But I guess it's not necessary especially for the isekai genre, which is the trashiest of them all, right after yaoi (even though I've read no yaoi, but how could it not be?).