Sometimes when people see others finding value in their discarded items, they see value again and change their minds! But who knows, maybe they were being truthful.
Finding these things can get kinda addictive, especially since you can make quite a bit of money! I wrote an article semi-similar to yours, only about selling though. Check it out if you’re interested!
https://medium.com/the-innovation/how-to-make-a-side-income-from-your-neighbors-3738397eaf1b