Reward, we are told, is inextricably linked with risk. Investors receive low returns from very safe assets. If they seek more, they must assume additional risk, thereby hazarding the possibility that they will receive less.
This is true, insofar as it goes. However, as Dr. Markowitz pointed out several decades ago, risk doesn't exist in isolation. If an investment tends to zig when an investor's other assets zag, it can stabilize a portfolio even if it is volatile. Conversely, a relatively tame security might fail to lower a portfolio's risk, if that security is highly correlated with the existing holdings. Context matters.