There's also a political motivation to use these drones. The Iraqi police, for example, don't trust that they'll get drones from the international coalition -- off-the-shelf drones put control back in the hands of the Iraqi government. Shia militias aren't as dependent, though. They also get military-level drones (such as clones of Boeing UAVs) from Iran, which backs at least some of these units.

No matter what, the use of drones isn't welcome by everyone. Militias have used the drones to target civilian areas, and that same ease of access has also led to many Syrian revolutionaries (some of whom are extremists) using the remote-controlled machines in the field. Even ISIS is believed to be strapping explosives to drones in the hopes of tipping the balance. This is more an example of the proliferation of technology than anything else. Drones are becoming mainstays of modern warfare, even among ragtag groups that receive little help (or sympathy) from the rest of the world.