In a car, you can control who is inside for the ride. You can pull over and throw someone out if you have to.
On a plane, you are trapped with potential crazies and there is no way out until landing.
That’s why I carry a couple of HVAC duct straps in my carry on. If we (passengers and flight attendants) have to subdue someone, I want a way to restrain them. Think a large economy sized zip tie.