User blog comment:Tricoro/Gifts Lucky Draw Mechanics/@comment-27468797-20160109154801/@comment-25968376-20160109162710

From a programming perspective, could be that the game chooses the prize for you already when it loads the boxes. That way, it doesn't have to make two network requests, which are costly and prone to errors. Thus, if you have a favorite box to pick, it might be that the game has already determined for you that you will get an egg.

But as always, if there really is randomness involved, we can't know for sure if we're just having bad luck or pure coincidences.