I’ve heard that putting clothes with buttons into the white mesh bags and putting the mesh bags inside the washing machine will avoid wrecking the stainless drum.
Not so much clothing with buttons that are a problem, although a button in the pump isn’t a good thing, but more small items like hankies, kids socks and the likes that cause a problem.
For small items that can become trapped or work their way between the drum and door seal, yes they are highly recommended. You can use a pillow case but I don’t think that that is as effective as the proper net wash bags.