Open Car Hoods

My neighbors have a strange habit. They leave their car hoods open all day long. If they're at home they go out and open them. If they're out and about, they'll open them as soon as they get to their house. If they were working on them, I could understand. If they were showing them off to people, I could understand, but they aren't. They just leave them open. They don't do this everyday, just on certain days, and when one does it, they all do it. Have I stumbled onto to some new covert communication system, like shoes on electric wires? Perhaps they don't want certain vapors building up under the hood?

Of course, it may just be redneck stupidity and they're opening them because sometime, somewhere, someone told them that on certain days it should be done. My votes still on the communication system.