From sources... Amazon is a heavy Java -> Scala shop. They are probably looking at Clojure to diversify as Scala is hitting some growing pains, but they can still leverage their large JVM expertise.
Parenthesis are always offputting to me, even though I like a fair amount of clojure concepts. I often feel like functional programming has made a cottage industry around putting obfuscated names around relatively simple ideas (see transducers for example)
I'm not directly in the dev space, but it appears as though the choice of languages that people use has far more to do with what Builder Tools will support than what people actually want to use. Teams only use Scala or Clojure if they are willing to build it using their convoluted Ant wrapper that doesn't make any sense.
Combine that with Scala's bewildering type system and I can see why companies move to Java or Clojure.
I was really into Scala and studying it and everything. I still remember all the scala bloggers I follow, Daniel, Tim MOrris, Paul Snively, etc...
Eventually I landed into a scala job role. Oh boy was it different. The other programmers were like type casting to Any or whatever that generalize highest type was (unified type theory).
The complexity is pretty high, it's great if you know it all but in all seriousness it was impeding...
As a Scala dev, that is absolutely terrifying. I can't even begin to think of a good reason for that.
(Ok, but in all seriousness... don't.)
Personally, I like the object + static typing + first class functions as it eliminates 90% of errors at compile time. If any error occurs at run time, am pretty sure it's logical. This is a huge plus. The only drawback - the ridiculous amount of type specific code you have to write for mundane changes/updates.
The Java community has its flaws (oh boy, does it) but it has adapted to the hordes of mediocrities. Give Scala to mediocre engineers (who typecast to Any, use null instead of Option[T]) and you have the Java hell with worse IDE support and 5x compile times.