One of the lesser reasons to wear a jacket even in summer is that a man needs a place to put his walking around stuff. There does not tend to be as much of that as a lady carries of course, since we are spared the need for a makeup bag. But though the virtual disappearance of smoking means the lighter and cigar or cigarette case are usually left at home, there are still quite a few things. My own fairly ordinary list of items was recently inventoried by the institution to which I was committed:
All of this requires eight pockets, two in the trousers and five in the jacket. That means that not just any jacket will do either. Those activewear things designed by someone who thinks that a man can get by with one interior pocket do not make the grade. I specify four interior jacket pockets alone most of the time these days - the extra storage makes space for a second wallet with travel documents when I am on the road.
None of this addresses the inevitable question of what to leave out or what to do when a jacket will not be worn. Unless at a resort or other place where all I need is a room key, my own answer is nothing - I carry all of it in a bag - but others will have their own solutions.
What's in your pockets?