[simonw]

Being built into the framework is a big deal, though.

The problem with third-party libraries for this kind of thing is that there's no guarantee that they will be maintained in lockstep with the underlying framework.

What if they get abandoned? Or a new version of the framework comes out with new features but the third-party library takes months to add support for them?

I think this may be an aspect of Django that isn't appreciated nearly as much as it should be: batteries included means that the feature you depend on are guaranteed to be maintained and documented at the same pace as the rest of the framework.