Personally I have nothing against it (or to be more exact - I've given up hope for a Javascript-optional web) but I see the argument of people who keep it disabled because:

– it consumes more battery and bandwidth (the latter still being expensive on mobile in some parts of the world;

– it's often used to track you (including tracking everything you do - mouse movement, things you type into forms without even submitting it, etc.), serve you ads, and so on;

– most security issues (XSS, browser-based 0-day exploits that escape the sandbox) rely on Javascript being turned on

– it overall slows down many pages with no tangible benefit to the user (this one is obviously not always the case, depends on the website).