It isn't about losing access to the tool, it's about lacking control of what the tool does. For example, suppose that the CMake developers, due to last-straw U

It isn't about losing access to the tool, it's about lacking control of what the tool does. For example, suppose that the CMake developers, due to last-straw Unicode bugs, lose sanity and decide that from next version (in a few weeks) an initial BOM and UTF-8 encoding in all files will be mandatory: are you ready to check and adjust all your source files and review your text editors (or to fork CMake)? More realistic scenarios include users discovering novel CMake bugs and changed defaults after updating CMake and developers discovering useful things that are impossible with CMake because of old bugs and limitations.