[forkhammer]

Well, they are buzzwords, yeah, but it's important to note that buzzwords become so because of their popularity and prevalence.

Why do you need model-view data binding? Emulating the responsiveness of desktop apps, for one, or having live-update capability. I wrote an app recently that let you add line items to an object, and the client wanted the cumulative fiscal information to auto-update without reload. I'd agree that the standard 'Hello, <your input content here>' example is overly contrived, but what about a field that calculates and updates tax owing as you type? That's not hard to write with just javascript, but when you do that about fifty different times in an application, having a convenient data binding mechanism is really convenient.

The other utility that I find quite convenient is DRYing up insertion logic--I hate that I often have duplication between server-side templates for existing objects, and some sort of client-side template for dynamically inserting new objects. Rendering it all client-side makes my life a lot easier when I want to add or change the surrounding template, and having the ability to do the initial render with a minimum amount of boilerplate is phenomenally helpful.

Those are two very real, very frustrating problems with which I feel any one of these frameworks helps a lot. I'm happy to go into greater depth if you'd find that helpful or revelatory.