I think that’s a very understandable reaction, and I had the same initially. But, there are upsides to using a proprietary format over HTML: 1. Encoding behavi

I think that’s a very understandable reaction, and I had the same initially. But, there are upsides to using a proprietary format over HTML: 1. Encoding behavior in custom components without resorting to Turing complete languages (JS), such that custom components (eg DatePicker) 2. Dependencies between components, like rules, become possible: If textfield A is empty, disable button B. 3. Access to native APIs that are not (yet) implemented in browsers.