When imported, most Converse sneakers have a very thin layer of felt applied to their soles in order to legally classify them as slippers. This decreases the tariff from 37.5% to just 3% as they’re no longer classified as sneakers but rather slippers.
To benefit from a lower tariff, it isn’t necessary to cover the entire sole with fabric. According to the inventors, “a classification may be based on the type of material that is present on 50% or more of the bottom surface.” (6,471,491) This explains why the “fabric” fuzz extends mostly around the edges of my shoes, where it can take up a lot of area without interfering too much with the traction of the bare-rubber centers.
This maneuver is known as “tariff engineering.” Another example is that toys representing humans are taxed differently than toys that are nonhuman. Due to this difference, Marvel argued in court that their X-Men action figures were not human.