Ask HN: Why are there no popular web frameworks merging front- and backend?

Dear HN community, I am wondering why I couldn't find any web frameworks which abstract the network boundary between frontend and backend. Developing in this kind of framework would feel like developing one single app, with a single entry point and a global namespace including both frontend and backend.

Are you aware of anything like that and I just missed it? Or is such framework just an unrealistic idea?