Well markets give a huge financial incentive for it. Before you had to get paid a bribe for an intelligence agent. Now you can just "legitimately" bet on a market. It's a LOT easier and more spread out, I imagine.
The existence of banks gives a huge financial incentive to rob them. That doesn't mean we should get rid of banks. It means we should create a huge disincentive to rob them (which we do). Same thing needs to happen to people using national intelligence secrets in prediction markets.
Banks are about saving money and reducing risk. Arguably when they got into high risk investments to make high reward is what contributed to the 2008 recession.
Not sure if banks are the best example of proving the country is not headed towards high risk gambling.