Stupid question: why do all the curves go down way before reaching a large percentage of the population? For example, California's curve peaks at ~900,000, only 2% of its population (and only a bit more if you consider cumulative hospitalizations). I guess 2% is not enough for herd immunity to kick in so what is it?

Edit: Oops, brain fart. Those numbers don't include all cases, just hospitalized ones.