Why would writing an essay about workplace violence prevention be beneficial to me?
If you are writing such an essay, presumably you are taking a class about business or management or some related subject. If you are taking such a class, it may be that you would like to go into that sort of a career. If you want such a career, then writing an essay (and, more importantly, gathering the information that you could use to write such an essay) will help you be more prepared.
If you are going to be a manager of a workplace someday, it is important to know what sorts of things cause workplace violence to occur. It will be your responsibility to prevent workplace violence as much as possible. Violence in the workplace could hurt your firm through lost productivity and even through lawsuits. Therefore, it is in the firms best interest to keep violence from occurring. If it is important for the firm than it is, by extension, important for you.
Writing such an essay, then, would be important because it would help to prepare you for a career in management.