Ask HN: Why is the JavaScript ecosystem heavily library based?

For instance, there is a highly upvoted post debating whether to learn VueJS or JQuery. And in general, in my experience, there is a huge dependence on JavaScript libraries for even the simplest of tasks. People almost view JQuery as a language different from JavaScript. I have never seen this kind of an environment in other languages like Python. Can someone give insight into why this is unique to JavaScript?