Related, Governors Island in NYC has a huge area called 'The Yard' [0] that's full of.. random hunks of wood and metal, pallets, rope, random tires and broken appliances. All for kids to play around in. It's just stuff a normal kid in a big city wouldn't get exposed to.
Maybe you live in more upscale cities than me but that all looks like commonly discarded stuff that some kids walking home from school would play with if they came across it.
[0] https://govisland.com/things-to-do/programs/playgroundnycs-t...