The point I'm making is not about NFZ's - my post is self-explanatory - people argue NFZ are too restrictive because drones won't cause damage. A plane hitting a drone is "avoidable" - you've obviously never flown a plane before.
I think the issue is causing mechanical failure to another aircraft. Here's a link to show how fragile the fins on a commercial jet engine are. A fleshy soft bird flames out the engine and causes an emergency. A lipo battery and drone parts would cause more damage.