Can you tell me how this is different from, say, Java? The fact that you are happy to run arbitrary binary code that was compiled for a specific platform? So now we are supposed to "write once compile everywhere" like C++, and then ship that to platforms? That is not in the spirit of the web AT ALL. If you want Java, at least THAT is write once, RUN anywhere. And why isn't running Java more seamless? I think answering THAT will be helpful to the original discussion.
Because ECMAScript turned out to be pretty awesome, and is now the de facto standard on the web.