Why React and React-DOM Libraries are Kept in Two Separate Packages

In a typical React project we import two packages, react and react-dom.

import React from "react";
import ReactDOM from "react-dom";

If we are using React CDN, again we add reference to two CDN links.

<script
  crossorigin
  src="https://unpkg.com/react@18/umd/react.development.js"
></script>
<script
  crossorigin
  src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"
></script>

Being a React developer for some time, a question might come to our mind. Why these two files are not combined and shipped as a single file?

React for Components

React library is used to create components. A component is a building block of an application. React library has classes and methods for this purpose.

On the other hand, React-DOM deals with placing the components on browser. It deals with shadow DOM and other efficient rendering techniques.

Now, if we consider React Native development, we again use React to build the app components. But we use React Native to build and publish the app for mobile devices.

The point I am trying to say is, React, as a component library is reused by several platforms like React Native, React 3D or React Art. That is why it is maintained as a separate project and package.