I've seen many variants of this diagram. What they ignore is that the dotted line is in practice much lower, so flattening the peak to the point where the health service can cope is approximately as hard as trying to stop the spread altogether. 1/ 
Given the number of hospital beds in the UK, I think the true picture is more like this. I.e., flattening the peak would result in a higher proportion of people getting treatment, but that proportion would still be small. So most people needing treatment wouldn't get it. 2/
I've already tweeted a calculation, but here it is again, slightly modified. If 40,000,000 get it in the UK over eight months and 10% need treatment, that's 500,000 needing treatment per month. If treatment lasts two weeks, that's 250,000 at any one time. 3/
The total number of hospital beds (mostly occupied of course) in the country is more like 170,000, of which 4,000 are ICU (mostly occupied of course). I don't know how many ventilators there are, but I'd guess 4,000 is the right order of magnitude. 4/
So even if we're very optimistic, I don't see how we'd be able to treat more than say 5% of those who needed it. So the effect of flattening the curve appears to be to reduce the percentage of people who have to do without from something like 98% to "only" 95%. 5/
Of course, one could try to flatten the curve much more. But that requires more or less the same extreme social distancing measures that one needs to cause it to decay, and herd immunity would take years to achieve, so it seems pointless not to adopt more extreme measures. 6/6
