MS let FFXI on Xbox but that was when Xbox 360 was just starting out and they wanted to get some kind of playerbase in Japan and attract more JP devs. What better way then having a FF title on their system.

Pretty much now that Xbox live is hugely popular. MS requires all games that have an online component to require Gold. Companies can't host their own servers must be done on MS's servers and there can't be cross play between other platforms. For FFXIV to be on 360 either SE will have to give in to MS's demands, requirement of gold, pay MS for servers and only 360 players can play on that server. Or MS can decide to let SE make the game have it connect to SE's own servers and not require gold. Which will probably never happen. When Tanaka was in charge talks broke down with MS after awhile.

You can't even use other pay services like Netflix, Hulu, Amazon Video, many more of their sports channels without Gold. You can't even use free services like youtube, facebook, or twitter app without paying for gold on 360.

MS has not allowed games to connect to non MS servers for awhile now. They wouldn't even let Portal 2 connect to Steam servers for leader boards and Steam Friend list and achievements and cross platform play with PC and Mac users, like the PS3 version can. You won't find other mmos on 360 now like DCU which is on PS3 and PC.

360 users playing with users that have their competitors console is a big 'No' in their book. Another reason could be it was also known that people that played FFXI often didn't have gold because FFXI was they only online game they cared about playing so MS probably thinks they are losing money because these players are getting to play online on 360 without Gold which they don't really like.