Implementing a new render target for React is not straightforward. It's essentially the same thing as inventing a new DOM that runs on iOS and Android. So why go through all the trouble?

First, there's a huge demand for mobile apps. The reason is that the mobile web browser user experience isn't as good as the native app experience. Second, JSX is a fantastic tool for building user interfaces. Rather than having to learn a new technology, it's much easier to use what you know.

It's the latter point that's the most relevant to you. If you're reading this book, you're probably interested in using React for both web applications and native mobile applications. I can't put into words how valuable React is from a development resource perspective. Instead of having a team that does web UIs, a team that does iOS, a team that does Android, and so on, there's just the UI team that understands React.