Elevator pitches are a great way to condense a complex idea into a small amount of time so you can get your startup project in front of someone who matters. Author Seth Godin recommends you pitch for a meeting, not the idea itself.
Essentially, the idea is to use that brief amount of time when you're in front of the powers-that-be to get a meeting so you can really pitch your project in full. Godin explains:
The best elevator pitch doesn't pitch your project. It pitches the meeting about your project. The best elevator pitch is true, stunning, brief and it leaves the listener eager (no, desperate) to hear the rest of it. It's not a practiced, polished turd of prose that pleases everyone on the board and your marketing team, it's a little fractal of the entire story, something real.
Of course, the elevator pitch isn't exclusive to elevators. It's useful when you need to pitch an idea -- any idea -- to anyone you want to work with. Godin's suggestion is that when you compress that idea into a two minute overview, the idea only loses a bit in the process. It also makes it a lot easier for someone to say "no". When you pitch the meeting, you're ensuring you get the idea in front of people who matter, and it becomes a real conversation as opposed to an announcement.
No one ever bought anything on an elevator [Seth Godin]