I think Square is against the idea of cash gambling in an MMO. Same with card games. They fear that (and probably rightly so), such competition will cause rifts in the community where players will get upset over losing. While I wouldn't personally do this, I could totally see many players losing a large sum of hard earned gil and cancelling their subscriptions immediately. Square is likely never going to take that chance.
I think this would also have the potential of increased RMT issues and could possibly violate gambling laws in some countries. Gambling with virtual currency is ok, but when that virtual currency can be exchanged for real currency, you wade into the deep waters of "grey area."
EDIT: Just to add, SE has already had issues with the Mog Bonanza in the past, since it was a lottery and viewed as gambling in some country somewhere. Edited, May 15th 2013 1:11pm by IKickYoDog
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