The 1/1 means the card itself is more rare, not the autograph. Of course, the autograph can't be "rarer" unless it has a certain inscription or something. It's the same reason a superfractor sells more than a base card, there's only 1 superfractor but millions of base cards
Collecting Reds and A's (especially Joey Votto, Bronson Arroyo, and Josh Reddick)