I think not only the Beginner's Luck but the main think which made profit is the fear of loosing the money. As so many times i have seen even now when ever i am betting with afraid of loosing the money in any new game in beginning i always winning but as the comfort level is going up or after 2 or 3 days play on 4th day it start to lose and until i find the reason i lost everything even the initial investment also.

So i think beginner luck is due to playing gambling in fear of not to lose the investment and that too playing without any strategy is giving profit but as soon as you start to use strategy and play and loosing starts it.