"That's a novel idea. BTW, why would you take your coat through security? Why would it not be packed? Seeing people dress and undress in airports is bewildering."
Here's one reason for you: I live in Houston. Currently i fly back and forth between here and Minneapolis every week.
The winter low (on average) in Houston is ~50 degrees. Hell, last Christmas day i wore shorts.
I think the high last time i was in Minneapolis was 40.
So, i'm going to be NEEDING a coat when i am in Minnapolis, but would sweat to death wearing one in Houston.
Thats why I'd be carrying it through security. Does that make sense to you?