String theory is not a monolithic topic and those who work on it are not clones. People differ in interests and aptitude, and their purposes vary widely. So who uses string theory, and what do they hope to get from it?
String theory also provides insights into physics beyond the Standard Model, which is fraught with unanswered questions. Using the stringy toolbox, physicists can explore the problems of strongly interacting particles. It has even led to developments in the world of solids and liquids.
Finally, there are those who examine string theory from a more abstract point of view: the mathematics on which string theory is based has become a fruitful and exciting field.