Because everything is open source and developed by different players at their own pace, and nobody can force anyone to do things a certain way. Plus everything evolves very quickly. Right now, for example, we need Babel because we are in the middle of transitioning from ES5 to ES6. Unlike, say, Python, we can't just take 6 years or more for that process.
I hear what you're saying kinda. It sort of comes with the territory since the web is a completely open platform, not a controlled/contained ecosystem like Java or even an open-source language like Python.
>Why is that?
Because everything is open source and developed by different players at their own pace, and nobody can force anyone to do things a certain way. Plus everything evolves very quickly. Right now, for example, we need Babel because we are in the middle of transitioning from ES5 to ES6. Unlike, say, Python, we can't just take 6 years or more for that process.