It seems like a way to let people not install an app. If there's always an app clip available, why bother installing? Many apps don't need to keep the audience engaged all that time - that's what apps are good at - with annoying notifications and all. If you are a parking meter provider, you don't care about that. You just want people to be able to pay you quickly.
App Clips will potentially be revolutionary in terms of app adoption. It's hard enough to get people to install your apps.
Now if you have a real life item pushing you in that direction, offering you a light weight app to start off with, it's SO much easier. I'm super excited about App Clips.