Why would anyone think that disease should not be completely eliminated?

The humorist, P.J. O’Rourke, said (tongue in cheek) that if we want to stop drivers from tailgating we should weld 6” steel spikes in the center of steering wheels pointing back at the driver.
Why does he think this would reduce tailgating?
Is his analysis based on opportunity cost or incentives? Explain.
Someone once said that economics tells us that disease should not be 100% eliminated from the earth.
Why would anyone think that disease should not be completely eliminated?
Is this analysis based on opportunity cost or incentives? Explain.