The specific reason not to switch to Jinja2 was that Django's templating language was originally intended not to be that powerful, so that you could feel reasonably safe handing it to non-technical "designers" or "writers" rather than fearing that they would generate a great variety of new tracebacks for you to look at.

If you have to ask why Django would not switch to (or even make any effort to allow the use of) any externally developed tool in place of its own, you might not have noticed that almost everything in Django is self-developed and that the officially given reason is that they are "perfectionists. with deadlines."

The reason why not is the Django project's philosophy