Many companies are using Distributed Erlang but not the way you described: they are using it to exchange messages between nodes running the same version of the software. Imagine that you are building a web application, you can directly exchange live messages between nodes without Redis/RabbitMQ [1]. If you are deploying a machine learning model, you can route requests through multiple nodes and GPUs without additional deps [2]. If you want to see which users are connected to your app, you can exchange this information directly between nodes [3].
In other words, there is a subset of distributed problems that Distributed Erlang solves very well out of the box: homogeneous systems working on ephemeral data. And some of the scenarios above are very common.
If you need to communicate between different systems or you need to persist data, then I 100% agree with you, I would not use Distributed Erlang (at best it would be one part of the solution). I think this distinction gets lost in many conversations and sometimes it leads to false dichotomies: "why Erlang when I have k8s/grpc/redis?" while in practice there is not a lot of overlap. I have written about Erlang/Elixir vs Redis [4] and vs k8s [5] for those interested.
[1]: https://hexdocs.pm/phoenix_pubsub/Phoenix.PubSub.html [2]: https://news.livebook.dev/distributed2-machine-learning-note... [3]: https://hexdocs.pm/phoenix/Phoenix.Presence.html
[4]: https://dashbit.co/blog/you-may-not-need-redis-with-elixir [5]: https://dashbit.co/blog/kubernetes-and-the-erlang-vm-orchest...