But drones capable of shooting down other drones - or aircraft of any sort - are much more expensive, for then it's not just a matter of software development and testing (which takes a relatively *long* time and is vulnerable to even small errors e.g. Boeing 737-MAX), but it's also a matter of having an airframe that can perfectly respond to that software and be able to carry armaments and dogfight in three dimensions.

This is why only high-end drones made by the best in the world (e.g. Lockheed-Martin) are even considered for aerial combat. Yes, they'll get better as time passes, but it's another example of the old debate between which is better, offense or defense. By its very nature, defense is reactive, adapting to new offensive tech and tactics...and while that defense is adapting, the offense is also evolving. Since the Industrial Revolution, only once has defense gotten the upper hand, in WWI - and even then only until the early months of 1918, with the advent of tanks and combined-arms tactics by France and the UK (but not so much by the US).