Office 365 is a poor example. The web interface has definitely come a long way, but any serious work falls over. Maybe they'll get there, but for now, local apps integrated with the cloud backend seem to work better.
Write now I definitely wouldn't want to try working with RAW photos from a DSLR or edit high bitrate 4K video using a web app. Maybe in ten years, but then again, those digital formats will probably have moved on to another level by then too.
Oh and email: there's still definitely a need for offline access. Be it a tradition MUA or when on a mobile phone. Online isn't online enough even for this.