Just to provide a data point: I'm hosting get-togethers of friends that you might call parties regularly and usually nothing or a very small amount is thrown away.
I'm wondering whether this might be specific to Germany. Here there is some social pressure to avoid wasting stuff (together with a strong trend for sustainability).
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.