This is why I have eight pens in my blazer. Yes, you read that correctly: eight.
In my early days of travel (a few years ago) I always took a pen with me from the hotel or airline (only the nice metalic ones) and put them in my left pocket of the blazer. they started pilling up until I had five and there was no more room for other ones. (and the weight is really a problem when you have more than five pens and something else in the pocket). I am happy to lend them to others but will watch them carefully so that i do get the pen back, as I’ve been using and seeing them for years. (Yes, they are pens and yet I have built a small sentimental relationship with them, heck I could even tell you by heart in whoch order (from left to right) what branded pen sits including when and where I got them. sue me).In my other pocket I have an etui that was gifted to me from the wife from my then recently deceased grand uncle. It was gifted to him by her very early in their relationship and he had it with him most if not all the time. I will never ever lend one of those three pens to anybody. Maybe the guy you described was in a similar situation.

In my opinion a pen is something one just has to have with him all the time. This is closly followed by a handkerchief and a pocket knife and maybe a lighter. (as well as obvious things like ID and a Credit Card)