A surprising number of conflicts: WW1, WW2, Korea, Vietnam, degenerated into artillery slugfests. You can't get much cheaper, faster, or more effective than guns shooting dumb explosives 20km away.
Only when the opponents were stupidly overmatched by US Air Superiority (Afghanistan / Iraq) did things change. But even with Air Superiority over say, Vietnam, USA still degenerated into an artillery slugfest.
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Its hard to beat 100lb shrapnel bombs delivered 20km away. Logistics wise, trucks carrying shells is just far cheaper than any other delivery mechanism. This fact has been true since WW1, and no technology has ever really changed the calculus. (Adding li-ion batteries, cameras, remote-control and other features so that you can turn the delivery mechanism into a drone is just unnecessary chips in most cases)
I just finished James Holland's Normandy '44 and I'd say, according to his book, that sentence pretty accurately describes pretty much all of the WW2 Normandy campaign as well.
(For the curious, here's a blog post from the Donbas separatist side that talks about drones and their combat use and maintenance, among other things: https://kenigtiger.livejournal.com/2140772.html)
However, Ukrainians have learned to embrace the drones in 2014-15 already, and have had a lot more experience with them since. Russia is still learning that lesson in the field.
https://kenigtiger.livejournal.com/2148946.html
(I would generally recommend this entire blog for those curious about the tactics and the logistics of the conflict, because it's one of those rare cases when a guy who is directly involved in the war, and has a long-standing reputation as one of the prominent hawks, is consistently writing posts that are critical of his own side - which criticism is far more likely to be accurate than propaganda from the other side.)
And dumb is cheap. Cheap can be king, especially if you can keep making them. The US had the same thing in WWII, the Panzer tanks were better than the Shermans in nearly every way - except cost and repairability.
1. You're selling them.
2. You have absolute complete superiority and are trying to minimize your casualties
There's a country that fits those parameters very well.
I guess, if it works...