Bonds are considered safer because short of the US losing WWIII there is practically no way the US bonds would not pay out or lose value. US Bonds are safe and predictable, backed up by the immense military and resources of the nation.

Investing in Apple 30 years ago would net a much higher return on $5k but even Apple was considered a unsafe investment in the 90s. On the other hand, Enron was considered a safe investment by many but went bankrupt almost overnight and shares became practically worthless.