Well, just the idea that you can use the entire core language without `#include`'ing any headers or depending on any standard-library stuff, is seen as a benefit by some people (in which I include myself). C++ inherited from C a pretty strong distinction between "language" and "library". This distinction is relatively alien to, say, Python or JavaScript, but it's pretty fundamental to C that the compiler knows how to do a bunch of stuff and then the library is built _on top of_ the core language, rather than alongside it holding its hand the whole way.

Your example with partial_ordering is actually one of my longstanding pet issues. It would have been possible (I wrote in https://quuxplusone.github.io/blog/2018/04/15/built-in-libra... ) to define

    using strong_ordering = decltype(1 <=> 2);
    using partial_ordering = decltype(1. <=> 2.);

But it remains impossible, AFAIK, to define `weak_ordering` from within the core language. Maybe this is where someone will prove me wrong!

As of C++14 it's even possible to define the type `initializer_list` using only core-language constructs:

    template<class T> T dv();
    template<class T> auto ilist() { auto il = { dv<T>(), dv<T>() }; return il; }
    template<class T> using initializer_list = decltype(ilist<T>());

(But you aren't allowed to do these things without including <compare> resp. <initializer_list> first, because the Standard says so.)