Good question so I looked it up "One of the most commonly believed reasons shoes are thrown over power lines is to signal the location of a crack house or prime drug dealing spot. Dangling shoes can also be the symbol of gang members claiming territory, especially when the shoes are hanging from power lines or telephone wires in an intersection." Or "Others believe it is done by bullies who steal a pair of shoes and put them in a place where they cannot be retrieved."
I had no idea!
I had no idea!
Well spotted Lesley.