Avoiding deeply nested component trees
By passing child components down instead of data you can avoid passing data down through many levels of components. It also makes your components more reusable. Even multibrand components become much easier to build. Overall it is a pattern which improves your frontend code a lot!
When building frontends you will pass data from a parent component to a child component. Often the child component renders this data, but not the component passing it along. The child components have different data requirements than your current component.
Then you add a new component, somewhere down your component tree. It has new data requirements, so you have to pass its data through all its parent components. On top of data, it might also need callbacks to provide interactivity. You also pass these through all parent components. You change a lot of files to add new functionality. With all the data passing the readability of your code also decreases. Overall the maintainability of codebase decreases.