When outbreaks get bad enough, the only option is a lockdown in order to bring the local pandemic back under control. Herd immunity through natural infection is a very dangerous proposition with COVID-19. The reproduction rate of the disease is about 2.5 and might be as high as 5.0, meaning that the threshold for herd immunity is somewhere between 60% and 80%. With the current case fatality rate, that means a LOT of dead people if countries were to let the pandemic rip with no interventions. And remember, there are more outcomes besides "mild case and you will be totally fine" and "you're dead." As we are finding, many people end up in the hospital, and even though they recover they require fairly intensive treatments and will have long-term if not permanent health issues as a result. Let the pandemic run rampant and you will overwhelm the healthcare system, which in developing countries is already limited.
No one wants to bring out the ban hammer of lockdowns. They are socially and economically disruptive. But if people don't follow proper social distancing protocols, refuse to wear a mask while in contact with other people, and go around pretending like this is no big deal, then lockdowns are the only alternative means of enforcing non-pharmaceutical interventions until a safe and effective vaccine had be produced and distributed. If and when that happens, THAT'S when we try to get to herd immunity - through vaccination.
