The hypocrisy of Job Interviews

[Eagles]

Let me preface this by saying I realize not every job interview/application follows this criteria.

I was listening the the radio and they were talking about how Calvin Johnson, Amobi Okoye, and Gaines Adams all admitted to using marijuana in college when they were interviewed. Although I do not have proof I'm sure there are many other players in the draft who have smoked marijuana in college but only the guys who were honest end up getting in trouble.

Frequently job interviews will ask questions like this to "test the character" of the person they are interviewing however they are hugely flawed because there is no rational benefit to telling the truth. Therefore the only reason why someone would tell the truth is because they are morally opposed to lying, so the people with the strongest moral compass end up being punished.

In fact the only value I could see in using these types of questions would be to see who tells the truth because those people are acting irrationally and you would not want them working for you(Although I doubt business do this).

Given that these tests are effectively useless why are they so common? Is it just another example of people acting illogically or is there some merit to these types of tests?

edit: I realize I missed something. Another reason someone might tell the truth is that they are simply apathetic and do not care if they get the job. Obviously you would want to weed people like this out of your business.