The primary role of adult stem cells in humans is to maintain and repair the tissue in which they are found.
Adult stem cells are a “natural” solution. They naturally exist in our bodies, and they provide a natural repair mechanism for many tissues of our bodies. They belong in the microenvironment of an adult body, while embryonic stem cells belong in the microenvironment of the early embryo, not in an adult body, where they tend to cause tumors and immune system reactions.
Most importantly, adult stem cells have already been successfully used in human therapies for many years. New therapies using adult type stem cells are being developed all the time.