it's not just the in-game currency. In an MMO a lot of the abuse comes from duping resources or items. If the in-game economy is secured by it's own ledger then duping resources to dump the market all of a sudden doesn't work cause the internal blockchain would reject any injected resources as they haven't been created in a mining process.
1 sat is just 1 sat so the currency is solid by design. It's everything else that gets exploited in game engines eventually resulting in a crashing eco-system. To go back to CSC MMO, the game had it's own scarcity engine which would ensure that ore, ships, module etc etc were actually created or mined in-game before ever making it to the market.
