An interview is just like a video guest post. When you conduct an interview with a person is just like liking him/her, but now they are more similar to share and associate to the interview. There are lots of pro when conducting an interview and the one who is getting interviewed is also benefiting from it.
Why there is a need for an interview? Well, it is too obvious that through it, you can send traffic to a site, but what is more essential is that it helps in making you have a well-established authority in your niche.