Conservative food use-by dates tend to generate food waste.

I would not blame the supermarkets so much. They will face public criticism when goods don't last to their "use by" dates.

It is no use urging people to learn and remember rules about how long food lasts. The fraction of people who regularly cook is much less nowadays, and those who don't do this won't be motivated to learn them. We will inevitably depend on what the supermarket says.