Why are widget-based web frameworks not so popular?

I'm talking about frameworks like Vaadin (Java), Wt (C ++), Reahl (Python), Agile Toolkit (PHP), etc. In my opinion, these frameworks are much easier to code (you code one language without needing to know JavaScript, HTML, and CSS) and to understand (the usual widget-based GUI approach is much easier for a noob to understand than MVC or MVVM). Why aren't these frames as popular as the regular ones? BTW, are there any such frames that I missed? For example, I haven't seen one for Ruby, Go, or other widely used web development languages.