They provided a bit of rationale (kind of sprinkled across the article).
For me using Next over CRA as a default comes down to three things:
- Batteries included, high utility components and defaults for things you ought to stitch together otherwise. CRA is not a drop-in replacement for Next, even if you only render client side.
- Flexibility. Your project might just look mostly static (fully rendered at build time) , or server rendered, or client side rendered. It rarely is. If you default to Next you can easily extend and configure these capabilities (and more).
- Great DX. It's a framework that respects developers with good documentation, flexibility and a "just JS/React" kind of philosophy. There is magic that you cannot easily break through as with every framework, but so far it seems they keep the magic boundary at the right place.