There is stdio, C++ wanted std::iostream there is string, C++ wanted std::string

Now there is blas/eigen, but C++ wants std::linalg.

What's wrong?

Unsafe C stuff to begin with, regarding stdio and string.

Yet another library that would be better served via conan and vcpkg, instead of putting it into std.

I agree with you. But what is the sentiment in the C++ community? I mean, other languages are profiting tremendously from package managers. In C++ things are going the other way - taking public libraries and putting in std (fmt, chrono, and all that).

Some of us think that ISO has had its time, C++ is getting this way because only those willing to travel and putting in the time to advocate for voting on their papers, are the ones driving this kind of features.

Additionally, contrary to other languages evolution process, ISO doesn't require that papers come with an implementation, hence why you get stuff approved, that only after the fact is proven not having been a good idea after all.

Coming back to your point, there is a growing community that thinks, that exactly because of this, it is about time to adopt at very least, the two biggest package managers, and there is now a C++ tooling workgroup.

However there is also another majority, from those that bother going to ISO, that think everything has to be shipped on std.