not all investors have the ability/desire

to maintain a 1:1 correlation with the S/P 500.

they might think that they do, but in reality studies will show the opposite. In fact, in a period of time between 1987 and 2017, the average mutual fund was up about 8% whereas the average investor was actually up 1%. Why is that? It's because people cannot handle that sort of correlation and when the index went down, they went "active" and jumped out of their investments ("flight to cash") and then when things had calmed down and they were confident again, they jumped back into the passive strategy ("buy high").

Look, I work pretty closely at times with Janus, Vanguard, Fidelity, etc and I am all too familiar with the active vs. passive arguments. The reality is that every investor needs to find their spot, invest, and then follow their own proper benchmarks and allocation adjustments (on their own or with an advisor). Just looking at one index is lazy and misleading.