Wearing your shoes actually helps prevent this. Basically every sneaker collector has (or knows someone who has) a story like this. The soles get brittle over time, and will fall apart if they have sat for too long. But if you wear them, it helps avoid that from happening. The natural flexing when you walk helps the sole stay flexible. If it has sat for years, it will shatter into dust as soon as you try to flex it.

Sort of like how cast metal is more brittle than forged metal. Because when you cast metal, it hardens in random or crystalline molecular patterns. So there is very little actually holding the individual molecules together, because every join where two crystals meet is a potential fracture point. But forging it into shape with a hammer will create a more sturdy piece, because the hot hammering forces the molecules out of those natural crystal patterns. By moving the metal around, the molecules are able to form much stronger bonds with their neighbors.

Anyone who has accidentally shattered a cast iron skillet by dropping it knows what I’m talking about. People expect metal to bend, because they’re used to thinking of forged metals that have been mechanically shaped while it was hot. But cast iron will shatter like glass, because it is just poured into a mold and the molecules stay wherever they were when the molten metal cooled, even if they don’t have strong bonds with their neighbors.