The point of an elevator pitch is to be able to describe your project clearly in just a few sentences. I've never considered the point to be, for example, getting funding in 90 seconds. Rather, it's a litmus test: if you can't describe your project succinctly in 90 seconds, you've probably got some issues. Those issues could be
- lack of clarity around what your project actually does - overemphasis on buzzwords - having a project that doesn't do as much as you think it does - inability to see your project from someone else's perspective
An elevator pitch should give your audience a clear understanding of what you're trying to build. It should give people listening or reading the chance to ask followup questions such as "How do you plant to build that?" or "How far have you gotten so far?"
Writing out a good elevator pitch is also a nice thing to have when building a landing page, or the home page for a project.