> 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.
buffers in the supply chain don't account for the wastage that goes on in western countries where people let food go bad in their fridge, or farms / grocers throw away cosmetically imperfect food.
This doesn't even get into the gross inefficiency of overweight/obesity where people consume extra calories that make them gain weight which requires them to consume extra calories to carry their surplus weight around, or the amount of energy that is expended just to move them around in automobiles because they can't walk or bike even moderately short distances.
There's a lot of wastage in how we produce and consume food.
Given that we have a policy of over-production, in good years we can easily afford to waste food like that — it's not like we were otherwise either going to eat it all (because developed nations already have an obesity problem in aggregate) or actually donate any significant part of it to good causes (though we could and I'd say we should, even if it's local rather than international e.g. the UK where there's a shockingly large number of people needing to use food banks while also having an overproduction policy).
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").