Yes, yes, yes... those are all "legitimate" and likely good uses of this technology, but they're most likely just additional/bonus tertiary use cases to the mai

Yes, yes, yes... those are all "legitimate" and likely good uses of this technology, but they're most likely just additional/bonus tertiary use cases to the main use case which motivated Google to expend effort on this feature: DRM. It's much like how web browsers' incognito/private mode is really useful for web developers and certain kinds of troubleshooting, but those are tertiary uses to the primary consumer use case for which it was originally built: browsing porn without leaving history behind.