Why it is asked at all
Because the thing being attempted takes longer than a life, and anything built to reward the people building it bends toward them in the end. Every movement that decided its own survival mattered more than its principles broke them to protect itself. The only guard we have found is to ask for the work from people who want nothing back from it, apart from the knowledge that they were part of a generation that seeded the new future for humanity.
And because it is not really a new sacrifice. Most people are already giving their time, health, attention and peace to a competition for advantage that nobody consented to and nobody wins for long. This asks for no more than that - only that it be pointed somewhere worth pointing it. Give up competing for advantage; compete at helping instead. Same fire, different target.