I'm not a Scala user, but Clojure the language tends to be extremely stable. Existing stdlib functions almost never get updated, unless they add a new (backwards-compatible) arities.
Releases tend to consist mostly of new features, and a small number of bugfixes.
Part of it is that the standard library API has been stable for years, where new things are added but no breaking changes are introduced.
The second reason is that Clojure libraries are typically shipped as source. This avoids the whole binary compatibility problem you see in Scala. Typically, you only compile the end applications to byte code.
I don't think so. It's because of a strong commitment to users not to introduce breaking changes. I've been mostly using Java and Clojure in recent years, and before that C/C++ and I'm pretty surprised people don't take backwards compatibility for granted, and that there are languages that don't consider it a top priority. (Well, new C++ compiler versions sometimes broke existing code, but that was quite rare)
Probably, more because its a lisp, whereas Scala was more of a fundamentally new language that isn't a member of such a well-studied family, but instead was led by inspiration from lots of different places, and has a lot more work in shaking out how to reconcile those influences into a coherent whole.
Though Scala being not merely statically typed by aimed at both interoperating with Java's type system and supporting a more robust and powerful type system than Java does did pose particular challenges.
No, it's because Scala's dependencies / libraries get distributed as compiled .class files, whereas Clojure's get distributed as source-code. Tried explaining this above: https://news.ycombinator.com/item?id=9807323
