A license only means something if you can enforce it. This means you can catch violations, and get courts to enforce it in a way that means something. If you can't catch a violation it is de facto allowed. What a license can restrict is limited by law, and so depending on the terms the court may say "you are not allowed to restrict that: they are allowed, go away". Or the court may impose a fine that is small enough everyone considers it a cost of doing business. How this plays out depends on the violation as well: if the violator can show they did their best to not violate that is very different from intentional violation. (I'm convinced the GPL will be broken - when a company shows they have lots of process to prevent the misuse, but a "rogue employee" hid their actions - the company will pay a fine but won't have to give their source code.)

I wonder how many of these drones deliver a .txt copy of the GPL along with their payload.

Only if you publish something.