Why use different camera angles?
Different angles are used for many reasons. Wide and/or long shots are used to establish the setting where the video is being shot.  Medium shots are used to show the relationship between people and/or objects.  Close-ups are used to see the expression on people's faces, or details like hand movements or manual operations (using a wrench or a food processor, etc.)

In interview situations, it is a cliche that you need a medium close-up on the subject. And if the interviewer is on-camera, then a similar shot of the interviewer is used so that you can see one or the other more or less full-face without the camera whipping back and forth and giving many viewers motion sickness.

Sometimes we will use the camera shot of the subject while the interviewer is speaking just to see the subject's reaction to the question or statement, etc. Or, conversely, a shot of the interviewer while the subject is speaking. This is called a "reaction shot".  And similar to occasional shots of the audience to give the viewer more of a sense of being there with the live audience.  And to see their reaction. Especially applause, laughter, surprise, etc.