Our minds need transitions to give us a "heads up" that something new is coming. Without the "heads up" the audience's minds will spend more time than you want playing catch up. Think of it this way. In your presentation, you are wanting the audience to do two things: realize the status quo that you are presenting, and have them leave with a new mindset on the situation. It is like you are pointing out two points on a map. Point A, the status quo. Point B: the new way of thinking. Without transitions in your presentation, you are simply pointing out the two points on the map and leaving it up to the audience to find their way from point A to point B. You are not giving clear directions.
When I'm in a new town and have to get from point A to point B, I can do one of two things. I can look at a map and try to figure it out myself or ask a person familiar with the area for directions. If I try to figure it out on a map, I may not know the shortcuts through town and I may run into some construction work on my way there. Even though I might arrive to point B, it probably would take me longer to get there than if I asked a local for directions. It the same with your presentations.
Without transitions you are forcing the audience to find their own way to point B. They may reach point B, but they may take the longer route to get there. With transitions you will be guiding your audience quickly and smoothly to point B. It will take them less time to reach to the conclusions you want them to reach. Plus, with clear direction, they are more likely to reach the conclusion you want them to reach.
Don't underestimate the power of transitions. When you're developing your presentation, be sure to work in smooth transitions so you can lead your audience effectively through your presentation.
