The obligatory shopping trolley

Why is it that shopping trollies are ending up in our streams and rivers?
Do they collectively attempt to commit suicide after years spent burning along supermarket aisles?
It is a sad end to see endless amounts of junk in our streams and rivers from trollies to tyres to old boots and computer monitors.
Its the trollies though which bug me because some people have to cart these miles from the supermarkets and dump them into a stream for really no good reason other than its fun and they cannot be bothered to send them back.
The supermarkets would need to advertise soon, for people who wish to shop there to first go to the local river and fish out their own trolley!