Uranium Fact: 1.7 Billion years ago there existed a natural occurring nuclear fission reactor.

Here are a couple of reasons:

• C and C++ projects often predate Gradle by decades they will not change their build system without a compelling reason.
• Gradle is written in Java and requires a Java Runtime.
• At least for C++, CMake has pretty much become the standard build tool.
• Dependency resolution on Linux was ‘solved’ by relying on the distribution. Today, there also exist package managers for C and C++ like vcpkg or conan and they also integrate with CMake.