Because it's a waste of time. All you have to do is look at Fox and it's plain as day that in no sane world will he be able to be a passable middle infielder. And yes, it would be horrible to have Fox as a fulltime OFer, 3rd baseman or catcher. He has been more than adequate so far at every position they have placed him at (except maybe C). He is not going to win a gold glove, but based on his play so far in the field he is definitely not horrible. He's definitely been tolerable in the very limited sample size so far. The only position he's come even remotely close to playing enough times to make a judgement call on is 3B and even that he hasn't really played for any significant amount of time. I'm not adverse at all for him to get the start when Aramis, Bardley or Soriano get their days off. I would never want to see him as anything more than the emergency catcher when it comes to being behind the plate. He was truly horrendous as a fulltime catcher before and I seriously doubt he's just "switched it on" in regards to the most important defensive position on the field besides the pitcher. That said, I would not be adverse to him playing catcher in the Fall or Winter Leagues since he at least has experience there and maybe he could shore things up even just a little bit where he could perhaps be the backup catcher if the Cubs still have him next year. That makes infinitely more sense than plunking him in as a middle infielder.