The reason is obvious. The human being must rationalize his kill. When that becomes impossible, he burns out. Add in reckless controllers and impossibly justified intelligence, we simply get a shoot first scenario as the only viable option. The way out is to resign forthwith and that is exactly what is happening.
These drones are powerful in support of troops on the ground who can provide local confirmation. Otherwise you are buried in information noise as folks must travel also. That noise is what an insurgency relies on to provide cover and target confirmation becomes very difficult.
Quite bluntly, these drones are been over used as a weapon. Their mission needs to be slashed back to gathering data which is equally important. How about providing eyeballs for their so called allies. Any patrol going out needs to be aware of known traffic. It allows intercepts and high patrol productivity.