When did the goal change from flattening the curve to preventing the spread? And is preventing the spread even possible?

So we flattened the curve, meaning we kept everyone from getting infected at the same time. This gave us an opportunity to develop testing, procure PPE/ventilators and kept us from overwhelming our medical system. We now know that the virus is too widely distributed and we will never contain it. if the virus is going to continue to spread because of sheer numbers, why continue the lock down? As long as the healthcare system is not overwhelmed and we do what we can to protect the most vulnerable what difference does the lockdown make? I am having difficulty understanding how any of this is going to save lives if the overall number of infections is the same.