Cash is not often useful, but it can be in two different scenarios.
Scenario 1
Suppose the LT bonds yield something like 3% with 2% inflation, i.e. 1% real. Suppose stocks yield a 5% dividend, i.e. 3% real, gold goes up 4% up per year, i.e. 2% real, and ST bonds provide 1%, i.e. -1% real. Hmm, cash doesn't look attractive at all.
Now suppose interest rates go suddenly up : LT bonds provide 10% and ST bonds 5%. Who's going to own gold ? A lot of people will sell most of there yield-free gold to buy these nice juicy bonds (either LT or ST). Who wants to take risks with a 5% dividend on stocks while riskless cash gives you the same yield ? I want at least 12% on my stocks now, and since actual dividends won't change, the stock price has to go down : a stock with a dividend of 2,5 € that was sold 50 will now sell for 21 €. The same for LT bonds : who wants your 3% bonds while the new ones yield 10% ? I'm okay to buy them back, but I'l pay them 30 € instead of the 100 € you bought them, so as to get that 10% yield.
Everything went down. Well, not cash actually, since cash is, well, cash, so its yield is close to 0 in any case. Well, you're a lucky owner of cash, so YOU can buy these amazing LT bonds and these generous stocks and this cheap gold. Lucky you. Some didn't have cash as it is a loser's asset.
That's a real scenario, it happened in 1981.
Scenario 2
Imagine a debt crisis. Debt levels are very high, either from governments, companies or even people, and the economy is slow. Earnings are not as high as expected, it's getting hard to pay back debts. The central bank does not want to print tons of money to pay back with cheap money, leading to hyperinflation, it wants people to pay back their debts at any cost.
Now money is getting scarce. You don't earn as much as you thought, because your employer fired you and you can't find another job, or your salary decreased, or the items you're selling as a company owner are hard to sell. But you have to pay back your debts. The only solution is to sell your assets so as to get cash, since cash is king. So everybody is selling their stocks and gold, and even their LT bonds, despite the guaranteed income (you need a lot of cash NOW, not it 10 or 30 years when you'll get back your principal).
So the winner is once again the cash owner. But wait ! If you have cash in a high yielding account in a not-that-safe bank, well... That bank may default and disappear with your cash when you need it so much !
It didn't happen yet (at least since 1972, the fiat-money era), but it doesn't look like Sci-Fi in Europe currently, does it ? In this scenario, that 4% CD does not look so gorgeous, does it ?
