Because "stop the spread" is a very nice goal, but not the actual one. "Slow the spread so hospitals can handle the load" is closer to the real goal. Without

Because "stop the spread" is a very nice goal, but not the actual one. "Slow the spread so hospitals can handle the load" is closer to the real goal. Without the vaccines, too many people get sick at once and more people start dying. On top of that, it's not just the vaccinations. Those who get the disease are also helping to slow the spread as they build their own resistance. There's been enough resistance to the vaccines that it's probably impossible to end this with the best possible result, so we're going for second-best now. And that still involves keeping as many people vaccinated as possible.