Why don't ants leave when they meet food that can't move?

The first thing to say is that these are biological laws, and you can't control them. Just as a field photographer can't intervene when he sees a lion killing a gazelle. This is their way of life. Back to the point. When ants meet food bigger than themselves, they will leave a sentry to watch. The rest ask other ants for help. Many ants brought back trophies. Like you said, even if ants die on sugar. With their persistent ideas. The heaviest ones will move away. I hope you stay out of it. Please respect the lifestyle of the animal kingdom. Thank you.