Shouldn't be an issue with bookies in licensed jurisdictions then... it's just a copout by the banks.

Rumour I heard was it could be due to fraud on loyalty programmes - deposit money to the TAB from credit card, take it out in cash that day, pay it back onto card, nothing spent, but reward points clock up. I do know of people that have done this, it was a reason that the TAB (NSW) dropped their online deposit limit to $200 at one stage.

More constructive action from the bank would have been to stop paying reward benefits on gaming transactions.