[maliker]

The thinner your backend, the thicker your frontend. I much prefer writing in backend languages (e.g. python) than in frontend languages (e.g. javascript).

And as someone else pointed out, you can't enforce security on the frontend.

The line is getting blurrier between front and back these days with new frameworks, e.g. React. Personally, I'm not ready to move away from mature languages generating HTML on the backend, even though it means giving up some interactivity on the frontend.