Well I personally think it's overhead. But i think a lot of transpiler things are overhead created to make languages / dialects more "accessible".
The principle idea is a very good - as always - it's to scope the problems inside the component.
so there are no "side-effects" to the layout :) so what's the downside ? you bloat the payload and you basically f*ck up heterogeneous systems.
the upside ? you don't have to worry that a change in the component will affect another component.
So as Uros mentioned it's a use-case thing. I personally try to program so that things are available to be reused in as many ways as possible which means ... no JSS but SASS or LESS.
same goes with inline CSS mutations and so on .... there are very specific trade offs and you really have to know what you're doing otherwise it just boils down to taste.