No way am I going to allow JavaScript from every single site using CloudFlare to run all at once.
If your browser instead presented the JavaScript as a program itself, and listed the programs it executed, and from what sources, users would have a wholly different perspective. JavaScript has the illusion of remote execution; most users don't think of it as executing programs on their computer.
Addons like NoScript are essential security precautions that mitigate a host of attacks. Unfortunately, even security-essential software like the Tor Browser Bundle leaves JS enabled by default because it'd "break" the web.
There's other reasons---as a free software user and activist, I won't run non-free JavaScript programs.
I gave a talk earlier this year about these problems and some ideas to solve them: https://media.libreplanet.org/u/libreplanet/collection/resto...
Using an addon like NoScript it's possible to selectively enable javascript per domain. When a website doesn't work without js I am forced to decide whether it's worth enabling js for this site. Very often I decide it's not worth it and I never use that site again.