The very limited number of exchanges essentially have an oligopoly, and as price climbs slowly the fall in price and 'runs on the banks' can happen extremely rapidly as the exchanges have no obligation to buy your coins for anything other then 'market rate' which assumes there's a buyer.
Oh, and market demand is largely driven by bots and speculators - not the actual functionality of the BTC network.
https://www.theguardian.com/technology/2014/may/29/bitcoin-b...