While the practice of publicly abandoning old shoes has been noted in multiple countries (including Great Britain it does not seem to have any set meaning attached to it and may be a simple form of imitation.
It is possible that shoes, being more sturdily constructed than most other types of clothing, simply last longer after being abandoned outdoors—leather shoes, for instance, are estimated to last for 25-40 years outside.
However, the opposite of this hypothesis is the commonness of obviously intentional shoe abandonment, such as shoe tossing, in which shoes are tied together by their laces and thrown in great numbers into shoe trees, over power lines, or over fences
In popular culture, a fisherman hauling up an old boot, rather than a fish, is an old comic-strip joke.