It's called environmental dumping. https://en.wikipedia.org/wiki/Environmental_dumping

First world countries ship waste to third world countries where dumping is not illegal (or at least not enforced).

You get stuff like this: https://www.youtube.com/watch?v=wVnMBGXVVUI

Stuff falls out of garbage trucks, trash cans get tipped over, stuff gets blown out of the bed of a dumptruck at the landfill, landfills erode and take trash with them. Trashcans aren't just magic portals that take trash into the nightosphere

a lot of single-use items come from fast food places, which people will eat in their cars and then just throw out the window as they drive along.

it's a fucking sad practice but it's really hard to get people to stop doing it, so the next best option is just to make sure as much as possible of the things you get from fast food joints will dissolve in a rain shower.