The jet engine is mounted to a plane. It's designed to withstand bird strikes without exploding - they literally blast frozen turkeys into it with an air cannon - but they can still cause engine out situations that result in crashes or emergency landings and risk the lives of the hundreds of people on board. Not to mention the huge repair costs all that incurs.
I value the safety of the people aboard that plane far above the comfort of the birds that would like to live at the airport, to the extent that scaring millions of birds is worth doing if it's likely to save the lives of a couple hundred people. Though that's getting pretty close to the threshold at which it ceases to be worthwhile.
Also, if I was in the bird's shoes, I would much prefer to be scared by a drone than ingested into the jet engine...