Yeah you can totally reinvent your component system yourself, or you can just use React which is used in production on thousands of websites and big products with top-level support of hundreds of engineers.
When you are into programming, like we are, you think of these things long before some big company tells you what to do.
Where I work, we use React because it's easier to find new hires (because they want to work with React) and quicker to get them up to speed on a project (because they already know the framework).
It's also easier to integrate and extend any 3rd party components, as we're already familiar with the boilerplate.