I don’t fully understand why drone operators follow these laws. Or any “no-fly” rules in general. Around an airport, it seems like common sense to not fly. Can’t someone just…buy/build a drone and fly is surreptitiously?
Woah woah woah, let's not encourage domestic terrorism here! Because they'll bring criminal charges and that's also what they'll call you so you better not get caught.
What if you're already flying when they enter your vicinity. It's pretty easy to do in a city. Also they may not announce themselves until you're already violating or even after when they charge you
Potential criminal charges are enough to deter most people.
Traditional, permanent no-fly areas tend to be enforced by the drone firmware (via GPS checks), so sometimes there is also a technological obstacle.
This is probably not the case here, but IIRC there are criminal charges attached to violating NOTAMs, so there’s still some kind of deterrence.