Because it makes it easy to interface rust, and takes the burden of a lot of boilerplate code you had to write otherwise to interface with the erlang distributed C-Headers for writing NIFs.

And Rust is memory safe and fast, C is just fast. Thats why Rust is so much prefered over C, though its possible to write NIFs in C or C++ as well, or even Pascal or anything else that is able to call into C and gets called from C. But not everything makes sense…

Erlang and Elixir are excellent glue languages, and excellent in handling a lot of network requests at once. You’ll be very hard-pressed to find another runtime that does these things so rock-solid and fast.

That being said, they definitely fall short if you need mega-fast processing that requires pure CPU muscle – like various matrix calculations, deep learning, image processing, those kinds of things.

People praise Rustler because, as @NobbZ said, it makes it very easy to integrate your own Rust code with your Elixir code. But that’s only if you need it. Most of the BEAM projects are perfectly fine being Erlang or Elixir only.

To learn elixir you only need to learn elixir.

Maybe later if you start doing some really, really cool stuff you might want to learn Erlang or Rust.

But at that point that’s a good problem to have … because you’re doing cool stuff