There's an argument to be made for having basic so-called leaf modules in the standard library. That is it makes it far simpler to get a basic installation of C++ and start doing cool things with it. Experienced developers or people that need domain specific features would be using their own specialised libraries anyway.

So instead of trying to figure out which one of the dozens of GUI frameworks to use in making a window and have it change colour, you just write it using the standard library. You want to do a HTTP request, then there will be code in the standard library for that.

It will also save work trying to figure out which third party library to use when you want to do these things locally on a small test project.