War is not only about doing the maximum damage, but also a trade-off of the risk vs. the reward. When Ukraine’s air defenses did not allow Russia to achieve air superiority without risking its expensive planes, they turned to drones. Aircraft are basically airborne artillery pieces which can also be used for recalescence and drones can be used for the same function.
Most of Ukraine’s drones are Turkish-made Bayraktar TB2 drones, which fire missiles the and US made Switchblades which are expensive and reusable, but Russia has begun using Iran’s Shahed-136 drones. These diminutive unmanned “aircraft” carry a payload of 80-100 pounds (as compared to the 1,000 pound payload of the typical missel) and have a range of up to 1,500 miles.
The Shahad-136 drones only cost about $20K each while the Russian Kalibr cruise missiles cost about $1M (or 50 drones for each cruise missile). While they are slow and noisy, they apparently can be precise enough to target the portion of a howitzer where the ammunition is stored and pack a punch strong enough to do some serious damage to infrastructure.
There has been speculation threat Russia is running low on their sophisticated/expensive cruise missiles, but the same speculation was floating around last May, so that’s still conjecture. What is clear is that Russia has an extremely worthwhile trade-off using these “kamikaze” drones because, not only are the targets far more costly than the drone, but, if intercepted by Ukrainian aircraft, even the missiles used to shoot them down cost far more than the drones.
While the occasional civilian building is being hit - highlighted by the Western media - by these drones, their main mission currently seems to be damaging the Ukrainian electric grid (and incidentally water supply by shutting power to pumps) and it’s possibly that the buildings are being hit by errant drones or some by those which had been disrupted by anti-aircraft efforts. Russia seems to be following a “scorched earth” policy when they are pushed back by Ukraine’s troops and it seems like they are projecting their power in a way which will make it difficult for Ukraine’s urban population to continue to live in the cities over the winter by destroying infrastructure rather than bombing the population.
There is speculation that Iran cannot produce drones as quickly as Russia is blowing through them, so this effort is likely not sustainable at this rate, but it likely takes longer to build generator facilities than to replenish drones.
One thing is certain, the strategy of future wars will be modified significantly based on the experience that militaries are collecting during this war.