I think it is not about web apps, more about the casual "one time visit" browsing. There is usually zero incentive to enable JS for a random website where you just want to read an article or watch images. JS there is usually (my impression) used for things that distract or try to lure me into other content. I like distraction free consumption. There is a high incentive to enable JS for a dynamic web app or site you regularly visit (eg HN) though.

Good control for JS and other requests in browsers makes this quite convenient to control as a (expert) user. I like umatrix a lot.