> The US throws away between 30–40% of its food supply.
Not just the US, sadly. One of the reasons they do it is: transportation costs, and to avoid the attraction of the homeless as it is "bad for business" ("makes us look bad").
Beyond that, there is also a good reason: farm output is variable, so a systematic policy of aiming for over-production means people don't starve in the years with bad harvests.
Beyond that, there is also a good reason: farm output is variable, so a systematic policy of aiming for over-production means people don't starve in the years with bad harvests.