I think the main appeal is that it would auto-delete the nudes you send to someone you don’t quite trust. I’m too sober to contemplate why you’d send nudes to someone you don’t quite trust, but I know it’s a thing.
Of course, once it’s on someone else’s device, Snapchat can’t really guarantee they haven’t kept a copy. From what I’ve read about the implementation, it doesn’t even try very hard. The fact that you can’t trust the client is basic network security.