Rushing to close a deal on a high value asset such as a boat, aircraft, or real estate where the seller insists on actual cash. Granted, you should probably use some form of durable check, but some buyers want actual cash. There are also cultural business habits in some ethnicity/national backgrounds to prefer actual cash over safer bank instruments.

It really doesn't matter: if someone wants to carry a large quantity of cash on a plane, this is still an open society and freedom must be defended.