This is a really strange thing to say. Erlang is still an event-driven I/O runtime, it just doesn't inflict the user with the burden of continuation passing like tokio does. What is the benefit of doing that yourself? Even with futures its far more verbose and awkward than it needs to be. And since the entire ecosystem is not built on this io system, you will always be finding libraries - even very popular ones, such as diesel - that are incompatible with it and forcing you into threadpools. Every library in use with BEAM uses async I/O in exactly the same way.