All the party NPCs (with the exception of Dog) will pick up items lying near them, on the ground. This becomes an annoyance when you purposefully want to drop stuff, which is why the developers added those bins. As you point out, they're cleaned regularly.
Actually they were added to get some ingredients for you tech gadgets. I used to run arround Tarant every morning collectiong rags for my cocktails...
Spick: You are playing as mage and the junk is for technologists.
