Something that can be discussed: Now if emacs24-erc is not installed, `erc' still is visible as a command, and fails when there is an attempt to call it. It is in the list of autoloaded functions: /usr/share/emacs/24.3/lisp/loaddefs.el:(autoload 'erc "erc" "\ To fail is not a nice behavior. The missing function: 1) can be made unknown; 2) can be made to give a message that a package needs to be installed :) 3) or the package can be made an obligatory dependency of emacs24-common (maybe, it's like this for some other subpackages). 3) can be justified that the reason for having a subpackage can be understood as the flexibility in changing the versions of the subpackage (from the main Emacs source tree, or from its maintainer). So, the reason can be thought no to be the ability to install less. Things are not very clear; this problem can be discussed more.