If I'm not mistaken ROOM (ObjecTime, Rational Rose RealTime) was also heavily based on it. I worked in a company that developed real time software for printing machines with it and liked it a lot.
replyI've worked on a number of systems that used Akka in a non-distributed way and it was always an overengineered approach that made the system more complex for no benefit.
replyFair, I worked a lot on data pipelines and found the actor model worked well in that context. I particularly enjoyed it in the Elixir ecosystem where I was building on top of Broadway[0]
replyProbably has to do with not fighting the semantics of the language.
Really depends of the ergonomics of the language. In erlang/elixir/beam langs etc, its incredibly ergonomic to write code that runs on distributed systems.
replyyou have to try really hard to do the inverse. Java's ergonomics, even with Akka, lends its self to certain design patterns that don't lend itself to writing code for distributed systems.