Interesting question. If we think about it, the number three is immensely significant for Christianity and other religions for the way that it implies perfect completeness and unity. This of course is most obviously seen in the idea of the Trinity, in which the Father, Son and Holy Spirit are united. Let us also remember that the first three numbers are the basis for all other numbers. However, I am not too sure if it would be pushing things too much to try to argue that this is the case in this excellent tale. Perhaps we would be better just to observe that having three points or groups of ideas in threes is a well known rhetorical device or strategy (used by Obama in his speeches as well as by others) that helps us to remember what is being said and reinforces the impact of the speech or story. Perhaps, therefore, this is why the series of different groups of threes in this brilliant story (the three friends and so on) adds to its narrative force and makes it distinctive.