Because cpp is not meant for "rapid prototyping" involving importing half of github with single command. And the reality is that it works.
C++ build systems are notoriously brittle. When porting a project to a new platform, you're never just porting the code, you are also porting your build system. Every single project is bespoke in some way, sometimes because of taste, but most of the time because of necessity.
It works because people spend a huge amount of time to make it work.
It’s the same build system for all of them.
Everyone know the system is brittle, but somehow manage to handle it.
FAANG, hedge funds/HFT, game studios