Here are 3 reasons I have come up with.
1. The first is obvious, the others not so. Content creates traffic with the aid of social media. The knock-on effect sees the traffic creating leads and these leads being converted into sales. Traffic spreads your message, your why and your expertise.
2. Smaller chunks of content can be woven into a framework. You own the framework even if you are introducing someone's content into that framework. A suitable framework can illustrate a concept. In NLP this is known as "chunking up". The best frameworks are visual. Example include Maslow's "Hierarchy of Needs" or Covey's "7 Habits of Highly Effective People". These two visual frameworks are based on triangles but there is no reason why rectangles, squares or circles cant be used. The purpose here is to aid in creating a relationship between the elements that compose a concept.
3. The third is the most difficult. By turning content into a belief, you can change peoples' belief and in doing so influence others. In essence this is what a good sales script does, at a lower level. But it doesn't stop there. You position yourself as a thought leader in your field.
........thing is, its not for everyone but it is food for thought.