Do you want to build interactive diagrams which are available via web?
Well, Visio SharePoint Services are there, but what if you want to go one step further than that and control/animate shapes more precisely and use standard css3 animations for example, or if you don't have / don't need SharePoint Enterprise?
The good old HTML/SVG export is here to help you with that! And yes, you can still have your diagrams in SharePoint. Or on GitHub pages. Or on your network drive 🙂