Because they originate all the blood cells in the body and many other accessory or support cells.
Because they are essential to cure bone marrow insufficiency (e.g. aplasia) because they replenish the blood.
Because they are used to substitute bone marrow in case of leukemia, myeloma, thalassemia.
Because they can produce enzymes that are missing in certain genetic illnesses.
Because they allow the regeneration of bone marrow after the use of high grade radiation and chemo-therapy in the treatment of cancer, a procedure which destroys bone marrow cells as a side effect.
Bone marrow hematopoietic stem cells have a key role not only in hematopoiesis, but also in the regeneration of organs and tissues representing an alternative to the use of embryonic stem cells in the research of a cure to all diseases that alter organs and tissues, like diabetes.