General numeric argument as in emacs is harder, since the only automatic parameter to commands is the focused window and even that is only for mouse actions; there's nowhere to stick it except ExtensibleState for other commands. Hypothetically a wrapper could repeat a command based on said state, but that's not necessarily how you want to handle the parameter in all cases (consider the question of whether the repeats start from the original state or the final one, when the command changes e.g. focused window; and worse when the focused window change happens only later such that you can't really do something based on it).