why is 40% of food being wasted in the US?

I recently read an article that stated up to 40% of our food in the US simply trashed. Over $165 billion each year is lost due to food going bad before we use it. Why are grocery stores over stocking their shelves if they know it will never sell and will be thrown away? Why are there so many starving people in this country and yet billions of pounds of unused food tossed in the garbage? Isn't obvious that they would have an idea (the farmers, grocery stores, etc) of how much is sold of something to give them a good idea of how much to buy? (based off of yearly statistics) Also, why aren't food companies donating some of this food to food banks? I read in the same article that if a name is slightly misspelled, or if they miss an ingredient in the food on the label it is thrown away. A poor starving person isn't going to care if something is misspelled they'll be grateful for the food. grocery stores shouldn't and don't need to throw away food that's on it's sell buy date, some of those items stay good longer and could be donated to feed the poor. (yes, if there's obvious mould it should be tossed, but I've had day old bread and it was fine). Also apparently if a fruit or veggie is too big or too small they can't sell it either, and these things are still picked and then thrown away, why not donate those items to feed the starving. There are millions of people in the US that are starving and they weren't going to buy those silly over priced items anyways so it doesn't even affect the business aspect.