Quick A: Because it doesn't have to be. It's "the C++ way" to prefer library solutions, and initializer_list shows how far you can get with a pure library solution, then the rest of the way with minimal language support to create initializer_list objects.

Recently on SO:

Why isn't std::initializer_list a core-language built-in?

It seems to me that it's quite an important feature of C++11 and yet it doesn't have its own reserved keyword (or something alike).

 

Instead, initializer_list it's just a template class from the standard library that has a special, implicit mapping from the new braced-init-list {...} syntax that's handled by the compiler.

At first thought, this solution is quite hacky. ...