That outfit on your skin is there to cover you up. In polite society, it's expected that you cover your skin with some kind of outfit — even if you have to wear something that causes you to incur damage, like circulation-cutting skinny jeans or a shirt with a really scratchy tag.

Another reason to cover yourself is to retain heat (ひ). Actually, retaining heat and staying warm is probably the reason people started covering themselves up in the first place.