I started using Snapchat after they added their dynamic filters. My kids, aged 2-7, think it's hilarious to have their faces warped or overlaid with funny images. My wife and I mostly take videos of them giggling while their face has puppy ears and then send it to each other and/or their grandparents.
I've seen older people (30+) use it to share trivial moments of their lives to people who don't live with/near them. The barrier to sending a disposable short moment is a lot lower than having a video chat or sending a permanent video file, so there's definitely utility to it.
