Because if someone gets hurt on a certain object, or eats a certain food, and they get injured or sick, then they can turn around and sue the trash company/entity who threw out said garbage, and win. At least in the U.S.A.... (America is already the most sue-happy country in the world, and the law for taking trash from receptacles or the dump proves that.)
Hmm, Really? I still don't really get it though. Never would've guessed that seeing as how the trash doesn't necessarily belong to the waste management company and it's not like they're gaining benefit like profit from either keeping it or letting others have at it. So I wouldn't assume that would make a worthy lawsuit. They're eating the contents of the trash at their own risk and know full well of the potential consequences ahead of time and it's not like they're paying for it to where it would need to be of a certain standard or quality. Kind of like how lawsuits against McDonalds no longer hold up when they're regarding getting sick or getting fat from eating their food. People know the consequnces and ramifications and are still choosing to eat it.