I think the main reason someone chooses to invest money into index funds is either they just want stable returns without too much hassle, or they believe in efficient market theory that basically states that you can't beat the market, so no point in even trying(and that's true for most of the mutual funds). But looking at value investors, it seems you can consistently beat the market.

Also, what bothers me about indexing, is that a lot of money is going into same companies(S&P500). Look at any S&P500 companies Top Institutional Holders and without a doubt Vanguard is on top(wild guess). Not sure what happens with the price, when company is excluded from S&P500.

In conclusion, indexing is fun in the bull market, it's just you can't retire in the recession years.