It is a locution taken from an ancient fable where the mice of a house are decimated by a cat, and in a meeting those propose to hang a rattle around its neck to hear it arrive, and thus give themselves time to escape. But when you have to offer yourself for the risky task no mouse dares, so the situation will remain the same for everyone. The phrase alludes precisely to the lack of sense of sacrifice for the group, to the very common position of prioritizing the particular good over the general, which in all cases is lamented, but is given as a fact. Especially when you risk your life in the heroic act.
