As a senior student in university, I have gone through many interviews -- interview to recruit new club members, interview for internship and so on. In my opinion, the procedure of recruitment is like choosing apples -- viewing resumes is like picking up apples, you can only decide the appearances, or in other words, whether there are obvious flaws. Interview is like the first bite, by which you know the real taste of an apple. But only by eating the entire apple can you see the core. That is to say, only by working with a person for some time, can you judge a person. So to me, interview can help us to get a basic knowledge about a person and is indispensable in recruitment but it has its limitations.
Interview is most helpful in the aspect that it provides interviewer a chance to observe something that resumes can not tell, for example, How the interviewee behaves? Is he/she nervous under pressure? Does he/she has excellent communication skills like eye contact? These things might be very important. Because some job might ask more than one's academic knowledge it might also require the ability of dealing with people and so on. Another important function of interview is that it can help interviewer to decide whether the interviewee lied in his/her resume. As we all know, under hot completion, in order to get more chances, some people tend to lie in their resumes about their experiences and so on. But in an interview, interviewer could ask questions related with interviewee's experiences. If the experiences are made-up, it's easy to detect. The last advantage of interview I want to list here is that it can be carried out in different forms for different purposes for example, pressure interview -- to see how a person react under harsh conditions, group interview -- to see how a person act in a team and so on. Thus, by arranging an interview in a particular form, a company can find out the person most suitable for the job.
But interviews have their limitations. You can not find out all about a person in only a few hours like that some apple might appear good and taste sweet but bad in the core.
In summary I want to point out that interview is an efficient way for companies to choose their employs but only by observing the long term performance, can you judge an employee.