This was one of the 1st things that shocked me when I moved to UK 6 years ago...the amount if food that is thrown away..and I'm talking food that it's not even close to expiry date..
The worst and ridiculous thing in all that is that on one hand Brits throw away food that someone can easily eat and on the other hand theyre collecting money for kids starving in Africa..I can't comprehend that!
Or as you say restaurants or shop throwing away food that could e.g feed homeless people.
I could never get my head around it.