Except that everyone who's sick has the potential to infect someone else. If you have a thousand people with the virus spreading the contagion to 2 people, then you have 3,000 in care and they have the potential to infect 4,000 more (assuming the first 1,000 are recovered and no longer shedding virus at that point).
In contrasts if you keep the infected down to 100 initial by keeping people isolated at home and going out only for essential errands, they can infect 200 people, who infect 400 people, etc.
Eventually everyone may come down with Covid-19 but if they do it slower, fewer people are in hospitals, hospitals have time to restock supplies, personnel have the time to rest and even to get sick themselves.
There's a simulation of that here:
https://www.washingtonpost.com/grap...FMtalJM3wsEgRx5Bt2vQTYklYXxzGbNLg0irWAxj5XImc