fear and ignorance: nearly everyone has an irrational fear of loss. it's called loss aversion, and it means that most people require 2:1 odds before they are willing to take a risk. e.g. in a fair coin toss, most people will refuse to bet until the payout is double the risk (i.e. they might lose 1$ or gain 2$). interestingly, the effect is based largely on how the risk is verbally phrased. if you describe the same scenario as either "a chance to win" or "a risk of missing" a payout, people respond differently (avoiding risk more than pursuing winning). that leads to large sums of money being left in savings, because people despise the simple idea of losing money (measured in dollars) much more than they like the idea of gaining something complex and abstract like "inflation adjusted total returns".

or

arrogance: some people believe they can predict bear markets, and chose to move assets away from affected markets before the bear strikes. in isolated bubbles (e.g. just tech stocks), then an investor might move to another asset (e.g. bonds, reits). however, in the last few decades the asset classes have become increasingly synchronized, leading to the potential for a simultaneous deleveraging in all asset classes, thereby making cash the best investment (e.g. it was #2 in 2008). this asset class synchronization has recently been dubbed the everything bubble.

fear and ignorance: nearly everyone has an irrational fear of loss. it's called loss aversion, and it means that most people require 2:1 odds before they are willing to take a risk. e.g. in a fair coin toss, most people will refuse to bet until the payout is double the risk (i.e. they might lose 1$ or gain 2$). interestingly, the effect is based largely on how the risk is verbally phrased. if you describe the same scenario as either "a chance to win" or "a risk of missing" a payout, people respond differently (avoiding risk more than pursuing winning). that leads to large sums of money being left in savings, because people despise the simple idea of losing hard earned dollars much more than they like the idea of gaining something complex and abstract like "inflation adjusted total real average returns".

or

arrogance: some people believe they can predict bear markets, and chose to move assets away from affected markets before the bear strikes. in isolated bubbles (e.g. just tech stocks), then an investor might move to another asset (e.g. bonds, reits). however, in the last few decades the asset classes have become increasingly synchronized, leading to the potential for a simultaneous deleveraging in all asset classes, thereby making cash the best investment (e.g. it was #2 in 2008). this asset class synchronization has recently been dubbed the everything bubble.