That's an understandable take in nearly all commercial and institutional contexts. But in others just involving human people, no. Many times JS does fail or isn't available. So building progressively enhanced web documents preserves utility across the spectrum of human visitors (and maintains accessibility). But if you only have a profit motive, then yes, there's no need for robust solutions. The amount of people that can't do JS well won't eat into profits or cause enough complaints to get you in trouble.
Failing to load is not a problem. Failing to execute is.
Usually because the web dev have used some new Javascript feature only $latest JS engines support. HTML and CSS if they're there they're there. Sure, there's caniuse for HTML and CSS. But they only have to load. The text/images/etc will be there. JS both has to be loaded and executed. If the later doesn't happen just right then the text and other multi-media won't be there. It's a very big difference.
