Because they reeked. In a v scientific study of 3 adult pairs of walking shoes left outside only mine were defiled and then destroyed.
So top tip, don't leave your walking shoes outdoors where there be foxes.
My question is, they were outdoors as they really were quite offensive, (I wear wore them every day), how can I get fragrant smelling shoes without using odour eater insoles? I bought some spray from the supermarket and it did sweet fanny adams.