The video isn't to see the product up close, its to see the founders. YC isn't selecting for charisma. Most founders (myself included) who submitted videos fumbled over our words and are completely awkward on camera. We also had no product to show at the time. What YC is looking for is that you're passionate about your project/company and that will come through regardless.

They're also looking for you be willing to step outside your comfort zone. As a founder you'll constantly have to do things that don't come naturally to you -- talking to investors or customers, interviewing employees, and even firing employees. The fact that you're not willing to make a 1-min video of yourself is a negative signal that you won't be able to step up and do those hard tasks that make you uncomfortable. Being a founder takes more than just being able to build the best technology.