I carry one. My wife does not. The guys at work do not. 99% of the people I know do not carry something as simple as a pocket knife.
That really amazes me. Don't know if that is cultural/regional thing or just peculiar to the folks you happen to know. Where I live, I'd wager the average man on the street will have a pocket knife of some fashion in at least 50% of the cases.
Just goes to show how we can not universally apply methods/ideas across the board. For instance, I've noticed in this thread...a concern for keeping a transponder separate from a key (to prevent theft). In MY case....theft is such a remote possibility that I literally give it no thought. The principle reason for having a spare ON the vehicle is so that my wife will not be stranded anywhere should she lose her key, lock it in the car or the key just stop working.
With that in mind...I need a key (already programmed and tested) on the vehicle in a reasonably accessible place that is absolutely protected from the elements. I disagree vehemently that a 3 button transponder key is weatherproof.
I have my own key to the vehicle...so IF a spare is ever needed and the vehicle is a reasonable distance away, we will use that one. The vehicle mounted spare is for emergencies ONLY and any inconvenience 'unwrapping' it will soon be forgotten.
Also, anytime we are going to be more than 50 miles from home, I make sure that I have MY key and she has her's. That way if one is lost/damaged we have a ready spare.
I consider car keys to be the same as a spare mag for my pistol: Two is one, one is none, things fail... (better to be prepared).