Erlang has its own HTTP(s) servers, like cowboy (https://github.com/ninenines/cowboy) so it doesn't need Nginx and the like. Those servers simply take the place of Nginx. There is nothing special about Nginx that you can't copy in other languages, like Erlang.
The main web framework for elixir, Phoenix, is just something that bundles cowboy (the webserver) with some utilities on top of it. No need for Nginx.
I do use Nginx in my side projects in front of my Elixir web app, but that's because of some conveniences Nginx brings (having Nginx is probably making my requests a little slower).
It's just Nginx + Phoenix on a rented Linode server. It's in beta, so I don't care much about security beyond the basics...
EDIT: I could drop Nginx and use "raw" cowboy (the webserver behind phoenix), but Nginx makes it easier to setup TLS certificates and I'm lazy enough to keep it around just because of that...
The main web framework for elixir, Phoenix, is just something that bundles cowboy (the webserver) with some utilities on top of it. No need for Nginx.
I do use Nginx in my side projects in front of my Elixir web app, but that's because of some conveniences Nginx brings (having Nginx is probably making my requests a little slower).