Let's put this in perspective

With regards to taking ‘assistance’ from question banks for exam preparation, I’ve been there too. However, it has, as it should be, been associated with getting mentally attuned to an upcoming examination. It’s important to get the brain ready for an exam in the format it’s to be taken. One example of this is how sportsmen (any sport, from athletics, to tennis, to swimming, etc.) get themselves ready, even psyched up, before an important event.
So, using question banks is a great way to get into the ‘exam-mindset’. However, making it a core for your exam preparation is preparing for failure!

Lets draw an analogy with sports. Any training coach will always have his/her player/athlete go through rigorous physical training and development programs run to a likely tight schedule, before even picking up say a racquet to strike a tennis ball. Why? When an athlete goes into an important event, just prior to the start, the adrenalin starts to pump; in anticipation of ‘the big moment’. No matter how much practice you’ve put in, no matter how many hours of training, nothing can simulate the experience just prior to what can easily be labeled a ‘make-or-break’ event. If your body is not prepared adequately through rigorous physical training routines, the surge of adrenalin, before and during the event, can quite easily result in a disastrous and potentially very painful injury; ruling you out for weeks maybe months. The strain put on the muscles and tissues by powerful and sudden surges of adrenalin, is tremendous; and has led to tragedy on the sports field on various occasions.

So, what’s the comparison with writing the CAR exam? You’re not seriously implying I’ll have a heart failure when I see the exam paper?
No. maybe not. But maybe I can guide you closer to an answer by asking you if you’ve ever had the experience of sitting in an exam hall for an important exam, with maybe a hundred others (or alone, which is scarier by the way!) around you, and staring alternatively between the question in your exam paper and the mosaic/marble tiling/carpeted flooring just above and beyond your question paper? You have no idea whatsoever, about the topic the question is about let alone the answer to it! Blank! “what do I do now?”?? Now that, is the effect of your emotional brain. Powerful? Oh yes!
So, you can read, learn, mug all the questions and answers in those question banks. When you get the exam paper in front of your eyes, you will likely have difficulty recognizing the question (which you will realize later, was taken out directly from the question bank you were reading that same morning!), let alone having doubts about the correct answer to it!
That is through my own personal experience and the experience of many others I’ve spoken to through the years. And that is why, preparing ONLY from q banks, is preparing yourself, for failure!