While AppCache is more broadly supported, future device integrations around Progressive Web Apps will check for the existence of a Service Worker. I’m not saying whether that is a good idea or not, but that’s what browser vendors have decided on. You won’t see the “Install…” badge on Chrome, for example, without the app having both a service worker and Web App Manifest.
That’s why it would be nice to have discourse use Service Workers when available or use AppCache for devices that don’t support it.
