It leaves you in control of the "show". If you have a series of pictures, for example, you pick when to move to the next photo, and can narrate as you do. You don't have to think about them flipping beyond the photos you wanted to share. They don't have to figure out how to work your phone.

It's certainly easier to pass around a phone, of course, but I can see the flaws.

This is a place where NFC would really be a step up though. Tap-to-share-screen, instead of having to find contacts and numbers and sending texts.