Just because something can summarize data doesn't mean it's the best tool to use when trying to explain something. Executives and VC's with non-technical backgrounds might be intimidated by someone using relatively complex tools for what, to them, could be a basic spreadsheet on a platform they know how to use themselves. Excel's value comes mostly from the fact that everyone knows how to use it at some level, and the formulas are relatively easy to follow, so your audience knows they could probably reproduce and verify your work.