I mean, this is the difference between a systems oriented language and a general purpose programming language. Rust would have the same flaw according to your logic. The idea of not including many of these things within the standard library is that in a systems language, having one specific json or xml library that's considered the defacto standard is very rare. For example, in C++ open source, there are several json libraries, like nlohmann, simdjson, rapidjson, etc. Not any one of these could effectively become a standard json library for the language, because each one of them has different tradeoffs and benefits.