It might be that they're not allowed to let you take things away. Health and Safety has a lot to answer for.
It's not so much H&S, it's the law. Technically anything you throw in your bin still belongs to you. When the bin men take the rubbish away in their lorry they effectively take ownership of your rubbish. Strictly speaking anything in your local dump belongs either to the council or the company that owns the dump. That means that you could be prosecuted for theft for taking something from a dump without permission. Stupid but true!
Yep, thats what i was going to say. And of course they earn cash on scrap metal value.