At present the browser monstrosity is used to (automatically, indiscriminantly) download into memory and run Javascripts from around the web. At least with a commandline web-capable JS runtime monstrosity the user could in theory exercise more control over what scripts are downloaded and if and when to run them. Perhaps more user control over permissions to access system resources as well (cf. corporate control)
1. One can already see an approach something like this being used in the case of
https://github.com/yt-dlp/yt-dlp/wiki/EJS
where a commandline JS runtime is used without the need for any graphics layer (advertising display layer)
What about people who do not own a TV