Historical accident, as until 1998 there was hardly any C++ standard library.
There was the C standard library that could be consumed by C++ applications, the C++ frameworks specific to each compiler vendor that sadly are no longer a thing, and the C++ ARM de facto standard with only iostreams, being used as the initial discussion for what would become C++98, a decade later.
Many of C++ warts are related to this historical evolution, like how many variations of string, arrays and other collection classes do you want to use in a single project?
There was the C standard library that could be consumed by C++ applications, the C++ frameworks specific to each compiler vendor that sadly are no longer a thing, and the C++ ARM de facto standard with only iostreams, being used as the initial discussion for what would become C++98, a decade later.
Many of C++ warts are related to this historical evolution, like how many variations of string, arrays and other collection classes do you want to use in a single project?