Futures is how big banks and the govt are going to get a hold of BTC from a regulatory standpoint. Since it is not actually feasible at this point to put restrictions on the actual coins themselves, the trading of them, etc.
Step 1: Buy lots of BTC on the open market with mega cash to push price up exponentially in a short time
Step 2: Open futures market and take out a massive short position
Step 3: Once futures market is open, dump large position into the price run up
Step 4: Sell short position for huge cash surplus
Step 5: Purchase BTC on the market for reduced rate
Step 6: Rise and repeat
Through doing this, large banks, investment firms, etc. will be able to accumulate the necessary BTC position over the coming years necessary to corner the market. Subsequently, these entities are also subject to govt regulations. This is how the govt gets a foot hold as well. As the price increases to very high levels over the coming years, the cost to miners will be astronomical and the transaction fees will be too much to handle. They will need a way to keep these manageable. Futures will offer protection to miners and will allow the common person to get involved as BTC will become more and more scarce.