A quantum security leap?

Take that network in Vienna, with single photons (the basic unit of light with quantum properties as discovered by Einstein) firing a million times per second along the fibre optic cables between the network nodes. Light detectors at the nodes spot these photons and determine a secret key from them in order to encode the data across that communications channel.

If a hacker tries to eavesdrop on that channel then they create a disturbance, according to the Heisenberg Uncertainty Principle, and the photons become scrambled which is enough to not only detect the presence of the hacker but to close down that communications link and instantly move to another before the data could be compromised.

Which leads us to pursue a rather obvious question: if it's so damn brilliant why aren't we all using it right now? No, seriously. Why hasn't quantum crypto arrived to enable us to all work happily in a world where data insecurity is a thing of the past?