This is not a hypothetical. Doctors are literally making these decisions everyday when they practice medice, and the CDC is also making these decisions right now in the context of the coronavirus.

It's based on the egalitarian notion that every human deserves a long and healthy life.

If an older person's life ends a bit earlier than it should have, it's sad. But a child's life ending premature, before they've had much of a life at all, is worse, by most peoples' calculus.

horribly utilitaristic invites 'one man's meat is another man's poison.' Lots of people think utility is a higher goal.