Testing is an objective and efficient way of gaining information on people. This information is normally not available from a discussion/ interview so it is new information and adds value to the process of understanding what makes you tick and your strengths.

Some Careers Advisers do not use any assessments at all to gain information on clients - most do. They use a wide range of questionnaires, tests and 'cardsorts' depending on which instruments they are qualified to use, which they prefer to work with, the clients budget, and the needs of the individual client.

An analogy (not a perfect one) might be a doctor who listens to patients and diagnoses ailments but does not have access to or choose to use blood tests / X-rays / biopsies to confirm their diagnosis etc.

Another analogy might be the recruitment department of a large business employing staff and relying purely on an interview and CV based discussion.

In both these situations I suggest that additional sources of information would add value (the prevalence of testing in modern medicine and the use of assessment centres, psychometric tests etc in business would support this view).