Professors, researchers, and teachers like to start their lectures with an extensive discussion of the background and/or context of an issue. Talking about the background is useful if it adds to the story, if it does not it is boring content that fills up those important first minutes of your talk where the audience is still sharp and awake.
Some examples of excess background:
- Tangents, side steps
- History that is important to you (when your company was founded), but irrelevant to the audience (unless you are a Champagne house that goes back to the 1700s)
- Preaching to the converted: spending slide after slide with data the audience is already familiar with, or arguing about issues the audience already agrees with
You are not giving a lecture in economics or history, you are trying to sell an idea.