Reason For Russian Drones

The use of Russian and Iranian drones by Russia in the war in Ukraine has been a particularly abhorrent feature in recent times.

The reason simply is reported now as desperation and lack of other weapons for Russia:

https://english.nv.ua/nation/use-of-suicide-drones-by-russia-indicator-of-their-low-missile-supplies-ukraine-russia-war-50278990.html

They are also an inexpensive option for Russia.