using the same directory drastically reduces the amount of assumptions about your system's permissions and your own installation (or lack thereof)
old school *nix editors typically do something like emacs and vi typically do, whereas old WinDOS/Mac single-user systems would have an installation file and a cache system-wide, and post NT and OS-X they have roughly the same but in a centralised user directory that is not system-wide, but is located as if it were (different evolution path)
using the same directory drastically reduces the amount of assumptions about your system's permissions and your own installation (or lack thereof)
old school *nix editors typically do something like emacs and vi typically do, whereas old WinDOS/Mac single-user systems would have an installation file and a cache system-wide, and post NT and OS-X they have roughly the same but in a centralised user directory that is not system-wide, but is located as if it were (different evolution path)