One silly yet simple reason could be the Not Invented Here Syndrome. For a company that size relying on Ericsson or Erlang Solutions for support could have been seen as something they didn't want to deal with. So they just wrote their own.
It is too bad though. Erlang, I think, has some features I like better such as hot code reloading, better supervision strategies, separate heap per lightweight process (hence no stop-the-world GC), and is battle tested for longer. Also, at least to me, actors with pattern matched receive, as central building blocks, makes more sense than channels. So I'll keep Erlang as my concurrent server side go-to language for now.
It is too bad though. Erlang, I think, has some features I like better such as hot code reloading, better supervision strategies, separate heap per lightweight process (hence no stop-the-world GC), and is battle tested for longer. Also, at least to me, actors with pattern matched receive, as central building blocks, makes more sense than channels. So I'll keep Erlang as my concurrent server side go-to language for now.