Similar airguns have been around a long time.
They are expensive, they cost more than many inexpensive firearms.
They require not only the gun, but the air tanks, the connections, regulators, expensive multi stage pumps, and other accessories.
Plus it is a rifle, long guns are not particularly popular with criminals because they are hard to conceal.
Did you look at the energy figures (although it has decent momentum, which I think is a better low velocity comparison, most people focus on energy):
http://www.crosman.com/mediacenter2/Guides/Crosman_Airgun_and_Pellet_Capabilities_Chart.pdf
It has the energy of a .22LR out of a rifle.
And it costs $1300 just for the gun. Add in the scuba tank, the connections, and some other stuff and you easily get in the $1,500-2,000 range.
So a $1,500+ 4 shot .22lr equivalent long gun is going to get popular with criminals?
A 10/22 is as powerful and has a much higher capacity for $200 new, less used. While being much simpler technology, easier to repair, more durable, and not requiring regular refills from a scuba tank.