Folks don't want to turn it on, because it's not needed for most cases and it's the perfect way (after flash and java) to get malware.

I don't know what's happening to web development, but since this app fever developers are fighting for eye candy and LESS accessibility. Sometimes I see a page that fails to work without JS, open the source and see just JS code. Where is the content? Web apps are often times also walled gardens, and completely break the functionality of the browser (based on linking, rendering text & images and using the back button).

Now even simple websites completely disable access to content just to show some silly animation.