The short answer is TIME CONSTRAINT.
The more you know about a topic, the harder it´s going to get to summarize your knowledge. So, take a lesson from the startup world, aim for a MVP. A Minimum Viable Product. How to get there?
Imagine you meet a friend on the bus? She is just getting started in the area of your expertise and wants some qucik pointers. However, she is getting off the bus in 5 minutes. You have time for three headlines max. and some bullets. Start you smart phone camera and do this exercise live.
Freestyle rappers and tech accelerators leverage time constraints. You shold try it. You will be amazed on what comes out...