Fundamentally, almost all "innovation" in browser and JS development for the last 20 years has been about giving new powers to website authors, not to the people actually using the browser. The idea of telling website authors "no, you can't do that" seems to be anathema to browser authors and standards groups. The result is that they make it easy for website authors to wrap their content in shinier and shinier wrapping paper and then tell users how great it is that they can now see all that shininess. Probably 50% of what a website can do today is stuff we would be better off not having available.