[Reelin]

It's a reasonable and well phrased question, so it's unfortunate that people are down voting it.

There are a few reasons as far as I understand it. Bear in mind how quickly our understanding of the virus (symptoms, transmission, infection rate & severity, etc) has evolved.

Initially, the only sensible thing to do was to attempt containment if at all possible. In my opinion, the US demonstrated a complete lack of preparedness and coordination here. Remember, we didn't know how bad it might (or might not) be. If it had turned out to be as deadly as SARS (it's not), things would be very bad right now. You have to assume the worst until you know for certain (within reason, of course).

There's also a preparedness aspect to things. Buying only a little more time can sometimes allow you to be much better equipped to handle the situation.

Then there's the logistical aspect. The tide may be inevitable, but how suddenly it arrives will make a huge difference in the quality of care (and thus outcomes) that is available to the few who exhibit severe symptoms. There are only so many hospital beds in the country, and we can only manufacture supplies so quickly. Imagine the difference between everyone in the country coming down with the flu on the same day, versus spread out over the course of a year.