found one mention of this by SE: http://forum.square-enix.com/ffxiv/t...=1#post1013009

Q15: Will we ever be able to transfer item/gil between characters on the same account and World?

A15: We currently have no plans to implement this feature do to various reason such as preventing RMT from abusing the feature.
so could be money, could be RMT. wish they would talk to us again about this since it's been over two years, and obviously this restriction hasn't hindered RMT significantly