The issue with keeping your emergency fund in an index fund is that the odds of your own personal crisis coinciding with a more widespread crisis is high.
I got furloughed in April 2020. Had my emergency fund been in index funds, I would have had to realize all those market losses in order to use my emergency fund, which would have meant my emergency fund would have been a fraction of what it actually was since it was in a savings account.
The issue with keeping your emergency fund in an index fund is that the odds of your own personal crisis coinciding with a more widespread crisis is high. I got furloughed in April 2020. Had my emergency fund been in index funds, I would have had to realize all those market losses in order to use my emergency fund, which would have meant my emergency fund would have been a fraction of what it actually was since it was in a savings account.