All about rate of effort and efficiency.
It is way better to use the cheap options first if you can achieve the same outcome, than to use your expensive options and risk losses to them.
For the cost of an F-35 jet (Estimated $100m USD a jet), you could buy 4000+ Drones, with 25kg carry capacity (avg price $10k-$50k, used $25K as estimate).
- 1 F-35 jet could carry in theory up to 8200kg in combined internal/external weaponry.
- 4000 drones in theory could carry a combined estimate of 100,000kg of small weaponry.
(20min delay)