The language has it's own built-in process manager capable of running thousands of concurrent processes with a small footprint.
Things like function arity and pattern matching are core concepts and core parts of how the language works. I've found that when comparing 2 simple web applications, one Python 3 and one elixir, that the Elixir codebase ends up being a bit larger because of the required boilerplate. However, as an application becomes larger, the disparity swings the other way and the Elixir codebase will remain smaller over time.
In addition, writing Elixir code just feels clean. Nothing really feels hacky, even if it is.