Look, you're kinda confusing things.

For instance, I work in a lot of projects with Django on the backend and Angular or React on the frontend.

The gist of all that stuff is: REDUCING COMPLEXITY. Tying your hands, so you can free your mind.

As Django and Rails are a way to better organize stuff on the backend, so are those frameworks a way to organize stuff on the frontend.

For instance, take React+Redux or Vue+Vuex: you bind all the transformations on your UI to a single object. All stuff that happens on the UI is a consequence of a transformation on that object.

So: 1) You just gained undo/redo, if you track alterations on your object. 2) You know the state of your application at all times, just looking at the object. You can also keep it and save it for later use.

Now, compare that to something you would do on jQuery. It is a great tool, but it wasn't built with that complexity in mind. So pretty soon you're dealing with actions happening in 5 different places. It gets way harder to wrap your head around it.