Institutionals use futures to hedge their other positions. What will they use bitcoin futures to hedge for? An unhedged future position is not an investment. It is a gamble.
That spot prices of bitcoin is lower than expected, making their current "buy mining equipment, hook it up, and generate bitcoin" operations unprofitable. Miners as a group will be net short BTC futures for the same reason that corn farmers are net short corn futures.
The longs will in because of the shorts - since carrying costs are so low, the futures will trade below the spot price, which means buy-and-hold BTC investors are better off rolling BTC futures contracts than the underlying.
http://www.investopedia.com/terms/i/institutionalinvestor.as...
There's a name for this effect which I've forgotten. But it can be seen, for example, in the markets ignoring the risk of nuclear war during the Cuban Missile Crisis. The reason is the same: there's no use in considering nuclear war in your decision-making, because you'd be dead anyway.
It's like saying bitcoin is a hedge against the end of the world.