Stem cell biology and regenerative medicine as an institutionally specified discipline is quite young, about a decade old. So it is no surprise that there is not a thing as a natural born stem cell researcher. All the famous researchers, the founding fathers and mothers came from other disciplines and studied something else as undergrads (just like in the case of molecular biology): they were veterinarians (like James Thomson, who received his doctorate in veterinary medicine), neurobiologists (Fred Gage), developmental biologists, biochemists, molecular biologists, classical medical doctors, bioengineers and so on.
All these people got immersed into stem cell research lately in their careers and so they carry their original motivations, disciplinary intuition and knowledge base when thinking about stem cells. This is the sign of an immature discipline but also good for creative ideas to enter. Historically stem cell biology and regenerative medicine will probably become a closed, paradigm ruled discipline with the necessary restrictions and less outsider innovations. The first generation of genuine stem cell researchers are years to come.
But today all stem cell researchers can become pioneers as they have the chance to form and invent radically new paradigms, not to live by them.