Have you noticed that most people don’t get right to the point in conversation? They ramble on a bit, tell stories, go back and add in a few details, and occasionally wander off on a tangent. Eventually they might get to the point, but not always. And in normal conversation, that’s fine, but in a job interview it’s a disaster - a very common disaster.
A job interview is not a normal conversation, so normal conversational style is held against you when you interview. An interview follows four very different rules than normal conversation.