I'm a game developer, and we thought at one point of using Bitcoin as the in-game currency of a space-civ type game. The main problem we ran into is security. We can't expect our players to all keep their own wallets and run a Bitcoin node. They could if they wanted to, but for the average player we'd have to generate a wallet for them and keep it on our servers. This means that in addition to a game, we basically also need to make and support an online wallet. Most importantly, keeping it secure, which is way outside our realm of expertise.

We figured we'd be the target for theft and it just doesn't make sense to take on that much responsibility.