Obito's MS allows him to be intangible. But when it attacks, his clothes don't get damaged at all (or fall off of him).
If we take the assumption that things really close to him or in contact with him are also affected by Kamui, does that mean that a person holding him or a backpack he's wearing is also intangible?
Clothes has always been a plot hole in Naruto. Like how Madara magically gets new clothes when he becomes SSOP. Or when the head Pain gets wrecked so hard by Naruto, but his clothes only get somewhat torn.