Why 5 Keywords? Why not 3 or 4 or 6?
Maybe this is a dumb question, but why 5 words and not 4, or 6, or 3?
Not at all Edward.
If we use too many keywords then we try to say too much, and if we say too much our story becomes diluted and can often say so much less. You can imagine that 10 keywords would be very hard to capture thoroughly and effectively inside a story where as just 5 would be much easier to represent in a strong way. On the other hand, it's hard to take a product or service and boil it down to just 2 keywords and think that would represent the full depth of the story.
So I imagine that we can see how too few or too many keywords can hurt us and limit our story, so the question then becomes how many is the perfect number.
Thus we use 5 because any less—like 2, 3, or 4—often isn't enough to represent the full essence of a story. For example we wouldn't be able to cover all of those questions we ask ourselves to develop our Purpose—who are these people, what are their strengths, what makes them different, how do they inspire us, and how do we want the audience to feel or what do we want them to do—in merely 3 words.
But we also don't use more than 5 because we end up trying to say too much. So five is perfect for answering the questions we ask ourselves concisely and being decisive in what meaning we want to convey to the audience. But it also is a number of words you can reasonably manage and recall in short-term memory as you quickly have to make creative decisions.