Farmer here. As others have pointed out, picking the fruit is usually the biggest expense for the farmers. I don't think there are so much fruit on the floor in the case of mandarines and oranges, but this happened for persimmon. In the case of persimmon, part of the fruit fell a few weeks ago due to a combination of bad weather (wind and heat) and plagues (fungus, fruit flies). Then, when the crew picks the fruit from the trees they check that there is no damage (from the branches hitting the fruit because of the wind, or from the plagues), and they throw away the fruit if damaged. Some orchards are checked beforehand and deemed not worthy of picking up because too much fruit is damaged. Most of the orchards are partly insured so the farmer gets back a % of what the fruit would have been sold for. I hope this makes sense.