Those who believe in Cryptocurrency claim it to be the next big thing in the history of mankind. The mere fact that Cryptocurrency is beyond the control of any government body gets it a lot of eyeballs. Imagine a universal currency beyond the control of liquidity, inflation and government subsidy. This would mean that the commercial activity of economies working on Cryptocurrency shall be privatized absolutely.
While “physical” delivery of Bitcoins as part of a futures contract would certainly be possible it raises regulatory and security issues in today’s environment where the cybercurrency exchanges are mostly unregulated, somewhat unreliable, and theft due to security hacks is distressingly common. By selecting cash settlement the CME and Cboe completely avoid the transfer of custody issues and shift those problems to somebody else—namely the market makers and arbitrageur.
Now, if that margin-call does not get filled and the price continues to fall, then I'm making profits on my contract but nobody is paying for it since the counterparty who got margin-called didn't get the liquidation order filled. So what happens is that at settlement time of the contract, that unfilled liquidation loss to the system will be deducted from the profits of ALL traders before they are distributed.
Note that you could just keep bitcoin on CryptoFacilities waiting to make the trade so you don't have to wait to move the bitcoin you bought over. This is called see-saw arbitrage model, where you keep funds on both exchanges to avoid having to wait. This is fine, but you can't ignore that there is extra capital being used in the play, so it affects your rate of return and capital utilisation. We will not use this method, we will do a full, complete, legitimate arbitrage process.