Unless they come from a field other than translation, translators usually start out as generalists, i.e., they're forced to accept assignments offered to them in any field of human endeavor, from nuclear physics to Sumo wrestling. Is that an ideal situation? No one, least of all a beginner, can be an expert in all possible subject matters, and lack of expertise will sooner or later come back to haunt the non-specialist translator in the form of misunderstood concepts and incorrect technical terms used.