That's because being convincing at interview is much easier to learn than writing good code or laying bricks fast. So for a bad coder (or bad bricklayer) it makes sense to train for interviews instead of training for the actual job.
One thing that is hard to work around is where the interviewee must demonstrate their skill first hand (e.g. implement FizzBuzz followed by strcpy and a binary search.)
Many common interview questions are too indirect (Show me a certificate; Answer this trivia question about a Java API from 1997) or misguided attempts at personality tests (How many sewing machines are there in West Virginia) all of which one can prepare for without having the actual ability to do the job.
These kinds of questions can still work, as long as they have not yet made it into "How to succeed at interviews" type books. Or when the applicants you want to filter out cannot resist outing themselves even with training (e.g. "Tell me about a time when you have been wrong / publicly changed your opinion" will probably always be a useful filter.)
One thing that is hard to work around is where the interviewee must demonstrate their skill first hand (e.g. implement FizzBuzz followed by strcpy and a binary search.)
Many common interview questions are too indirect (Show me a certificate; Answer this trivia question about a Java API from 1997) or misguided attempts at personality tests (How many sewing machines are there in West Virginia) all of which one can prepare for without having the actual ability to do the job.
These kinds of questions can still work, as long as they have not yet made it into "How to succeed at interviews" type books. Or when the applicants you want to filter out cannot resist outing themselves even with training (e.g. "Tell me about a time when you have been wrong / publicly changed your opinion" will probably always be a useful filter.)