You couldn't be more wrong about cartilage- that is one of the keys to a great stock! A great stock is the ingredient of a great sauce.
Bones come in different shapes and sizessmall . Small bones from birds can be eaten whole without extra cooking. Ends of bones from cooked meat can often be eaten (and taste great).
Benefits: Bones contain minerals. Cartilage contains cartilage (glucosamine, etc), marrow is healthy fat.