Because so far I just can't see react as the best/simplest approach to dragging REST[1] apps into the world of GUI COD(Code on Demand)[1] apps. Vue seems to strike a much more elegant balance, for example.
Especially in terms of life-cycle - I can't say I'd look forward to maintaining most complicated js stacks for say five years - with a horde of (rapidly evolving) dependecies, and often a plethora of build tools/steps that in general all do some rather simple, but incompatible source-to-source translation (templates to html, some js dialect to another, scss to css).
Vue certainly doesn't fix all of that - but it seems a bit more consistent and simple IMNHO.
But maybe it's just me. It'd be interesting to hear if anyone's actually made the jump from "react in anger" to "vue in anger" - or vice-versa?
[1] http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
Even with years of front-end experience I see these engineers fail at creating a reliable, documented and structured architecture. I guess, that's because they don't have time, budget or are no longer used to fiddle around and explore third-party projects (which is actually sad).
That is, getting started with Angular (or Vue, I expect) is easier and you will get something together faster. I expect the reason why React is so popular to be the mix you describe - although "templating" is a bit off, because JSX isn't templating in the PHP or JSF way.
From my personal point of view I can say, that I never regret the decision to switch to React (from Angular/Backbone.js). Especially the simple structuring (basically a component tree) is incredible simple compared to what you had in Angular 1. I am leading two projects with six digit LOC in the front-end and it is a pleasure to see how quickly new member can contribute, how clear the architecture is. Because there's no magic at all.
But that's all very personal, opinions differ greatly and I even know one developer who loves Angular 2. But he also has to work with Hibernate in the backend and compared to that everything is great - just kidding ;)
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Edit: I have read Fielding's paper for my B. Sc. thesis a couple of times and it's a great piece work. Should be a mandatory lecture for a lot of fields.
With Vue, on the other hand, it was easier to get started. I got a prototype working in a week with no previous knowledge of the framework. I'm avoiding the component state and using a Redux like approach using props and a centralised state, and I didn't even need to use Vuex[1].
I'm using typescript, which helps catch a lot of bugs early on, it's a little difficult to integrate with single file components[2] (which are awesome, btw), but once I got it working, it proved to be an excellent combo.
The documentation is cristal clear and very beginner friendly. If you're getting started I highly recommend using vue-cli[3] to bootstrap your project
I think Vue sits between React and Angular, being simpler than Angular, offering more features than React, and easier than both to get started.
[1] https://github.com/vuejs/vuex