Because covid19 is a pandemic while every single one of the examples given were at best localized epidemics.
More importantly, countries who endured SARS epidemics such as South Korea were very fast in issuing decisive tactical lockdowns and rolling out policies devised to contain the spread. Those countries who never endured similar epidemics did not had the infrastructure in place to act cirurgically to contain the epidemic, so their only option is to impose a nation-wide lockdown.
More importantly, countries who endured SARS epidemics such as South Korea were very fast in issuing decisive tactical lockdowns and rolling out policies devised to contain the spread. Those countries who never endured similar epidemics did not had the infrastructure in place to act cirurgically to contain the epidemic, so their only option is to impose a nation-wide lockdown.