Aren't market crashes defined as events where the entire market crashes. In such cases even the index funds would have lost value. Didn't the crash of 2008 affe

Aren't market crashes defined as events where the entire market crashes. In such cases even the index funds would have lost value. Didn't the crash of 2008 affect almost all stocks (and perhaps even bonds) ? Not everyone has the forward runway of 20~25 years. There are periods of 20 years that gave little to no return in the stock market [in other words a loss]. "Sufficient time" might be long enough that I am on my death bed by that time. The opportunity cost of waiting in the hopes that the prices will some day pickup can be substantial.