Coronavirus Disease 2019 (COVID-19) Pandemic

The problem is not how lethal the virus is, but how many people need to be hospitalised, especially in intensive care units. The health care organisation of any country would be completely overwhelmed by a large scale epidemic. As you saw, the situation in Hubei was extremely critical at a point they needed to build brand new hospitals and to send doctors from Chinese army, and only 0.12% of the entire population was infected. So the main goal is not to have more cases than hospitals are able to receive.

There is also a mid term goal: avoid that the virus becomes a new seasonal flu, and in order to obtain that, we need to eliminate the virus from the entire human species, and be sure that the potential future epidemics coming from infected animals will be quickly stopped. This goal becomes more difficult to reach if numerous humans are infected in many countries. Eradicating a illness caused by a virus is quite difficult because it is highly able to mutate and to resist to the vaccines we may produce - and this is why flu still exists and why we need to produce new vaccines every year. This new virus already mutated by the way, since the Italian one is already different from the Chinese one. Another danger is that when two different viruses meet, they may exchange genetic content. So imagine someone who is infected at the same time by an ordinary seasonal flu and by Covid19. A brand new virus could be created in his body, then transmitted to other humans. So we don't really want that Covid19 helps flu viruses (or simply other quite harmless coronaviruses) to become more contagious or more pathogenic. Another scenario is a mutation where the virus would for example become able to infect pigs (their genome is very similar to ours, so it wouldn't be very difficult), and we would have a dangerous situation where a virus would be able to circulate among humans and one species they tamed.