Because boring and stable is good. I'm not a Django fan (Rails guy here) but it's battle tested for years, there's tons of support for it, it supports server-side rendering (not just a backend for React, which god help me if I ever have to touch that POS again), and even better people know and trust it. Go look up Meteor.js and the conversation around it 10 years ago, sounded the same, but gone and never to be heard from again.