Good luck?

It seems almost customary to wish someone "good luck" upon hearing that s/he is going to have an exam or test. Why is that so? Even I have succumbed to this social trait. Perhaps luck is indeed needed to pick out the correct answers for multiple-choice questions. Perhaps it just sounds better to wish someone luck. Or maybe it's just "Singaporean" to accept whatever is done by others and not question the motives behind it. Going by my last argument, it seems perfectly fine for me to fall prey; I'm Singaporean after all. But I refuse to use such a lame excuse.

It sounds so phoney at times. It really does.