With great respect Mickey:
I understand salt, water and fingerprint sweat is softer than barrel steel as well.
Its not the abrasion or wear that steel wool can cause (I agree with you, it isn't appreciable inside a barrel, but it can and does easily scratch blueing on the outside), but if I felt the need to use steel wool, I'd also feel the need to oil the snot out of everything immediately!
Steel wool dust and fibers attract a pile of moisture and can rust quickly, because its pretty cheap steel matter.
I don't see the need when better options are out there. Perhaps living in a humid area, I've seen steel wool still in the package with some rust. Using it (not on a gun) looked like going down an Alabama road