When the legend callys first came out, they were the top ball available. I believe it was set up this way so that mult-accounters couldn't win a bunch of credits at lower tiers then just gift their other 'legend' account the Legend ball. <<<<< how I see it, anyways...
Now that we have the Nike balls without the tier restriction it makes no sense. Atleast make it available for a Legend to gift another Legend those Callways.