The issue is scale. These guns can likely be deployed for big events etc but how do you effectively protect the airspace around airports, powerplants, or other critical infrastructure with such devices?
Use cameras, acoustic sensors, and RF receivers to detect a drone's presence, and use a phased array antenna to shit some appropriate jamming signals in its general direction.
Your local electronic warfare military contractor should be able to set you up with all the equipment you need for such a system.
I've read about training birds of prey to kill drones, seems dangerous for the bird to me though.
Joke aside, is not far from being a real tactic, deploying the so-called "defender" drones, which are guided by a autonomous system, fed by an array of sensors around the perimeter.
I can see myself developing such a system.