Should not, true, but in the case of many websites the reality is that allowing JS means you lost your privacy. Just like one cannot allow webgl and canvas by default any longer. Thanks to all the web devs who helped creating this web dystopia.

You can't go out in public naked and just ask everyone to look away. If you want someone you don't trust to run unvetted general purpose code on your machine you have to accept that you are trading away some privacy. You can sandbox them (wear cloths) but that doesn't give you strict privacy.

Implement it then.