Why do investors invest in index funds like Fidelity Spartan 500 Index -LRB- FUSEX -RRB- where the expense ratio is 0.10 % and not in Vanguard S&P 500 ETF -LRB- VOO -RRB- whose expense ratio is lower -LRB- 0.05 % -RRB- despite having the same return ?
What is the best and lowest expense Ratio ETF fund family ?