Fewer available hosts leads to less opportunity for the virus to mutate, and the less successful a virus can be in causing illness.
Won't we reach herd immunity just as the virus runs its course? Why do we need to be vaccinated?
The sooner our immune systems are prepared to fight off the virus, the COVID infection outcomes become less severe, and the virus has fewer opportunities to mutate into something vaccines don't help against.
Our numbers are declining, and if there's a chance the virus will just mutate, why should I get this vaccine now?
We have to start somewhere, and stifle the opportunities the virus has to mutate any further. There is a possibility that an annual COVID shot may be needed to defend against it, similar to an annual flu shot.