Because you buy at a given yield, dictated by the coupon and the purchase price / maturity. Duration (sensitivity to interest rates) affects the price PRIOR to

Because you buy at a given yield, dictated by the coupon and the purchase price / maturity. Duration (sensitivity to interest rates) affects the price PRIOR to maturity, not at maturity. If you buy a bond at a 5% yield to maturity, and there is no default, you get earn that 5% period. You don't have to rely on somebody else believing that instrument is "worth" a certain price, the company pays it or they are in default and can potentially be forced into bankruptcy. Yes, default risk is a real risk (more in the high yield space than IG), but that is a much lower risk than volatility you can see in equities. Just to be clear, I'm not saying stocks are bad, they typically always earn more in the long run, but they are volatile, much more than bonds.