The more emotional we are, the more we tend to generalize. This is because our thought patterns become much more reactive and less analytical when we are upset. Asking specifying questions forces the speaker to become more analytical and thereby more rational. Asking questions has another effect besides improving your understanding of the information. It also creates rapport.
Relevant questions show interest in what the speaker is saying.
When the speaker perceives you are interested, it creates a feeling of mutual respect. This is an instant rapport builder. There is little that is more frustrating than the feeling that someone you are talking to isn't listening. This feeling is most likely to emerge when the listener is a passive listener. There is nothing that will destroy rapport faster than having clients believe you don't listen to them.