It depends on the keyboard layout. Some (US) do have it like you described, but others have the dashes reversed.
Both make sense, to a degree. On the one hand you can argue that the em-dash—being longer—should require and extra key, but on the other hand it has more uses so it should not have the extra key to be more accessible.
Both make sense, to a degree. On the one hand you can argue that the em-dash—being longer—should require and extra key, but on the other hand it has more uses so it should not have the extra key to be more accessible.