Betting on the outcome does not make social attacks more expensive. More like the opposite, as it’s incentivising on the conflict, not adding a cost to creating one. Did sports betting stop any match? Surprisingly for some, people in favor of the new proposal are actually putting effort on creating a fork, instead of just gambling on the situation. In my opinion, that’s what takes the cost. Moving fiat is easy, but showing computing power is expensive. That’s why btc works by proof of cpu work, not proof of stake.