Once you get to be about 35 or older you begin to realize that your parents were actually, gasp, young themselves at one time. That's if your parents have turned into rather straight-laced grown-ups who seemed to never want to allow you to do anything when you were a teenager. You begin to realize this, but it's a vague concept. Not one you spend a lot of time contemplating.
Until you find something like this old jacket.
It's likely pretty safe to assume this was something done by Dad or a buddy when he was in the Navy during WWII. Makes me wonder where on earth he wore it, if he actually did.