The focus of browser development was(and always has been) a kind of Worse-is-Better thing of supplying sexy features to wow users. While client apps are defini

The focus of browser development was(and always has been) a kind of Worse-is-Better thing of supplying sexy features to wow users. While client apps are definitely sexy, the overall shape of the browser wars was towards throwing in many bullet-point features of varying utility and complexity - so, not just JS, but JS plus CSS plus additional media types(including plugins). Once you have a client scripting thing with traction, it sucks the air out of the room for a slightly-better client scripting thing. And this could be said of ActiveX, Java, and Flash - they did not keep traction based on what they did better than JS, but what they did that was simply impossible in JS(which mostly amounted to I/O access or certain media types).