While you may be right, the difference to me, and the main reason why I originally asked the question, is that USD has the full force and guarantee of the us government. AAPL has a discounted future cashflow. Gold has industrial, sentimental and government consensus value. BTC has none of that, just a consensus of value based on active trades, which (side note) may well be the best thing about BTC.

I recently sold my little stash of BTC because I just realized that I don't understand at all what is happening regarding BTC, why it is happening, and whether it will continue to happen. All this BTC has no where to go but into other prospective wallets. I also had a sudden concern that there is no reason to trust Coinbase, let alone the market or BTC in general, and why would I leave money with people I have no reason to trust and have no means of penalizing should they fail to honor their terms with me.

The reality, as others point out, is that Coinbase has people dumping real money into their system to get in on BTC, and thats what Coinbase use to pay my withdrawal, which is as simple as I could have imagined it. I just dont know why.