I have worked for restaurants and supermarkets, and they throw away food in abundance. In the factories I see how tons of food go to the trash, someone "recycle" the defective packages, others throw it all away, it is cheaper.
I try not to waste anything, maybe it is because of how I grew up... I like to use the oil from tuna cans to make mayonnaise, some say it is dirty, but I love the taste.