Why would a company want to integrate BTC to their game when they can just use their own currency?

Xbox Points, Fifa Coins, WoW GOLD etc... They take your money and convert it into a currency which you can NEVER SPEND ANYWHERE ELSE. That is the most important factor. They don't want you spending that money anywhere else. Using BTC would be the exact opposite of what they are trying to achieve. If you think any company is gonna allow you to withdraw in-game currency to pay for your car you are mad. That is exactly what they fight against.

Now 'Gaming' on the other hand (I mean gambling), Yes BTC could be huge.  Right now many companies are struggling with anti-gambling regulation around the world. Using Bitcoin they can subvert that process.