The main culprit for the throwing away of edible food is the rise of the supermarket over local shops and the 'nanny' culture that we find ourselves living in.
When I was growing up we lived in a village. There was a butcher, a baker, (no candlestick maker) and a greengrocer. There was also a convenience store, but we didn't shop there as it was much more expensive than the other stores. Everything came home in unmarked wrapping. Fruit and vegetables in brown paper bags, meat and bread wrapped in white paper. No best before, no use by. If it smelt good and looked edible you ate it, if it was a funny colour or smelt bad you threw it away.
As we got older the local shops closed. Supermarket shopping became the norm. Foods had 'use by' and 'best before' dates. My father's constant observation to my teenage self was 'best before, not poisonous after'. So now I still try and keep to that principle. Meat and dairy I'm more careful with but fruit, veg and processed food - if it looks good and doesn't smell funny then it probably doesn't need to go in the green bin (yes, at least our council composts food waste).
I saw on a TV show (I cannot think what I can have been watching - I think it may have been Justin Lee Collins) a couple of blokes who practised 'Freeganism'. This is going round the food waste dumpsters of shops and restaurants and liberating the food that is still edible. It was amazing the stuff they were finding. Certainly enough for them to live on. Interesting concept, although given the pigeons and other vermin in London not one I'm sure I'd like to try myself!
Certainly some chains (Pret a Manager springs to mind) do operate a similar type of scheme in as much as what they don't sell on any given day is distributed to charities at the end of the day. Perhaps more initiatives like this should be in place, and not just from sandwich chains.
Packaging is another irritation. Buying things in plastic trays, wrapped in more plastic; or in plastic cartons inside plastic bags inside cardboard boxes. Again my sole comfort is that where I live all of these things are recycled when I throw them away; but that doesn't happen everywhere and packaging could and should be reduced.
Food, just as much as everything else, is a limited resource; more so as the planet's population grow and typical crop cycles are effected by climate change. Food needs to be thought of in terms of sustainability just as much as all other resources like energy and water.