They are faster to render especially when resizing the window, and they work in the exact same mental model of layout as everything else in CSS: the box grows t

They are faster to render especially when resizing the window, and they work in the exact same mental model of layout as everything else in CSS: the box grows to fit its content. Flexbox and grid do not subscribe to this: flexbox shrinks/grows its content to fit itself. Grid is a configurable beast, something in between, and also makes it possible for grid content (not the container) to define how it itself is laid out.