One important reason is compile time. C++ stdlib headers are so entangled which each other that each one brings in tens of thousands of lines of complex templat

One important reason is compile time. C++ stdlib headers are so entangled which each other that each one brings in tens of thousands of lines of complex template code, which may increase the compilation time for a single source file to seconds, and it's getting worse with each new C++ version. Also, it's not like writing your own growable array is rocket science, and a simple, specialized version can be done in a few dozen to a few hundred lines of code.