Need to run parallel tasks? Go serverless.
Caching? Try Redis.
Messaging? We've got a service for that, too.
By the time you're done shopping for services, you've got a good 'ol distributed system spread across all of these services. Welcome to a set of new problems that you didn't experience with your simple little app on its own.
Elixir is a hot new-ish contender in the (so hot right now) functional programming space. It's like if you could run the syntax of Ruby on top of the battle-tested reliability of the Erlang runtime (the BEAM). With the Erlang runtime, you get so many tools built in for free.
The following chart really shows the difference in tool-choosing that you end up with (hat-tip to Saša Jurić's book Elixir in Action for this).
I'm very new to Elixir, at least in actually building things with it. But from the perspective of someone who gets distracted easily (like most of us, right?), I think having the opportunity to sit down with a suite of tools within arms reach instead of having to go shop around as I need them... I think that can only be a good thing.