Sperry duck boots toddler size 10

Two pair of Sperry duck boots. The cream ones are in pretty good shape, not worn often. The cheetah print ones have some pilling on the rubber part, not sure why but my adult ones did the same just this style with them cheetah. Never had the problem with any other Sperry boots. You can see the pilling in the picture. Both boots are Toddler Size 10