You have been thinking about your app for 2 years, before this moment when you are ready to talk to investors. You have grand visions of the bigger picture, and how your app could become a major platform in your industry.
Investors have not gone through this process, and see many pitches that claim to be a platform in your industry. You can't skip the part where you actually explain what your app does, now, today, in very practical terms.
This serves 2 purposes:
- The investor actually understands what it is you do, after which she is ready to try to understand your broader vision for the future
- The investor can develop a gut feel about whether a user today actually would like to use and keep using the product. Inside an investor pitch, there is always a mini (customer) sales pitch