Erlang isn't a popular BEAM language outside of companies and by this point Elixir has probably taken a good chunk of that just by capturing people outside of that context enough as well.

With that said there is almost no reason to use Elixir, it doesn't provide enough on top of Erlang to be meaningful and Erlang as a language is considerably easier to learn, so if you onboard people you'll have a better time. Erlang also has less features you probably shouldn't use and you'll end up with more simple, straight forward code than with Elixir in the long term.

For people who like a bit of order in their programming Gleam is a better alternative to both of these; it just has a regrettable view of OTP, the libraries around processes do not seem very well thought out with regards to providing a similar experience to Erlang/Elixir when writing `gen_server`s, for example.

I don't know of any. People are really just selecting for the underlying runtime. And Elixir and Gleam are better targets here.