I believe that most of modern Web frameworks that pretend to be MVC ones also has a notion of data binding in one form or another. Examples: AngularJS, EmberJS, KnockoutJS, etc.

I am assuming that "data binding" is a declarative definition (oxymoron, no?) of live link between data (a.k.a. model) and its representation (a.k.a. view). With some transformers in between (a.k.a. controllers).

I understand why declarativeness is kind of appealing but also understand that as usual it comes with the price. In particular: 1. Live binding is quite heavy, either with dirty watch (high CPU consumption) or with Object.observe() (high memory consumption with high CPU load in some scenarios). 2. There is a "frame" part in the framework word, means there are some boundaries/limits that can be hard to overcome if you need slightly more than it was designed for.

Quite usual time split: 90% of features are made in 10% of project time. But 10% rest take 90% of project time. I suspect (a.k.a. educated guess) that those MVC things are not helping to implement more functionality in less time... If so their usage motivation is not quite clear.

As an example: last week wanted to find virtual list idea/solution. Found one in vanilla JavaScript that is 120 LOC. Implementation of the same but in AngualrJS is about 420 LOC. Most of the code there seems like a fight with the framework itself...

So is my question: what benefits that MVC stuff or data binding give us? Is it just a buzzword popular among project managers or they give us something useful. If later one then what exactly?