A few reasons he has explained multiple times.
He likes the switch-hitting aspect Fowler (and Edman) bring to that spot.
He likes Wong down in the order to lengthen the lineup after the meat of it.
He agrees Wong has the numbers for it.
And then there's the thing no one will say, but we can mention it here.
With Wong, there is a sense that maybe it's best to let him alone when he's playing well, like he is now.
Change him, and he might feel the need to change, even if he doesn't try to.
Personally, I'd like to see what Wong could do up there.
He knows his numbers are prime for that spot, but he's not going to campaign for it, like he probably would have done in the past.
It's puzzling to me that the Cardinals have limped through a season with one of the league's worst leadoff production and not given many chances to the guy whose production (and speed) has screamed for a chance since June.