In order to avoid depending on any additional libraries and parsers, CMake was designed with only one major dependency, the C++ compiler (which we can safely assume we have if we're building C++ code). At the time, building and installing scripting languages like Tcl was difficult on many popular UNIX and Windows systems. It can still be an issue today on modern supercomputers and secured computers with no Internet connection, so it can still be difficult to build third-party libraries. Since the build system is such a basic requirement for a package, it was decided that no additional dependencies would be introduced into CMake. This did limit CMake to creating its own simple language, which is a choice that still causes some people to dislike CMake. However, at the time the most popular embedded language was Tcl. If CMake had been a Tcl-based build system, it is unlikely that it would have gained the popularity that it enjoys today.