r/TheLastOfUsHBO:

u/xander707

The point is that with the cure, humanity as a whole has a nearly guaranteed chance to avoid (cordyceps-related) extinction. Maybe not 100% of humans will get it, but it will spread far and wide and allow humans to more easily propagate, rebuild, and over time dominate the planet again. Whereas without the cure, they live in a constant struggle, and even what small, well defended communities they manage to build are in a state of fragility as infection is a constant threat that could cause their collapse. A cure wouldnt fix things overnight. It may take years, decades even, but eventually humanity would make a strong comeback.