People change with time, and the audience on social networks also goes through changes in their lives: jobs, activities, hobbies, acquaintances, religious or political views, children, marriage, divorce, retirement. You get what I mean.
You can change too. Your company may begin to offer new services, expand its product line, find new opportunities in your niche, or be so successful in using social media that you grow a new audience that feels the need for your products or services.