If you're a regular guy, you're likely to react by becoming bored and tired. If you're doing sinister stuff, there is a chance that you might start to stress out from the interaction. I believe similar techniques are used when screening people for government security clearances using a polygraph. They seem to push people hard and accuse them of lying. I can only assume it's with the intent of causing legitimately guilty people to "crack".
I am not trying to justify the practice, just speculating about the purported rationale. Not a very fun experience as an innocent person.
The takeaway I got is that they just don't want people to visit Israel and made it as difficult as possible for me (which involved taking away my personal documentation, such as my invitation letter and copies of my citizenship, to give me a tough time when I got to Ben Gurion).
It was bizarre.
But then, I'm Jewish Israeli, so I don't have a lot of first-person experience with the full interrogation experience, just second-hand accounts from both sides of the table.
They tried to intimidate me with their faux "all seeing eye" - asking about whether or not I trained judo (in reference to the jiu-jitsu Gi I had in my luggage) but aside from that, the questions about the shekels in my wallet and also taking issue with the rubber waistband on my pants, they didn't really ask about anything else. The shekels thing and the issue they took with it was just absurd.
It was really just civilian employees on a power trip trying to mess with me... because they can.
The interrogation interests me. It sounds you don't feel it was useful? I had heard about this kind of interrogation over mundane stories, and understood it as a way of "testing" individuals' stories (especially under duress). But that would depend on it being repeated/prodded thoroughly, which it seems isn't the case.