Most of my sailing is racing, & our rules require all persons on board to wear a PFD. The last couple of years, I wore a vest, but now am looking for an inflatable. The vest is a PITA when you're railmeat & constantly going under the boom.
When out for a day sail, sometimes I wear it, sometimes I don't. When racing, I wear my team shirt, but when out for a cruise, I like to wear bright orange or hot pink or something really highly visible as well. If I go overboard, I want to be seen.
New York State has some kind of requirement regarding life vests for all on board certain boats during colder weather that I read about recently, but offhand I don't recall what it is.
Hey Soft - welcome to SN dude. Your sig is hilarious.
As for the answer to the OP - since our lake is very sheltered, we adults rarely wear PFDs. The kids wear them any time they are out of the cabin.
But just today, I made a dumb decision. It was only blowing 10-12. Pretty mellow conditions. I was going to go forward to unpack the genny. I grabbed a vest, but then thought, "Ahh - I'll be fine." Threw it back into the cockpit and went forward.
Sure enough - I was fine. BUT I still should have worn the vest on the deck. I mean really. It's always when you think everything will be fine that an overweight goose falls out of the sky, beans you on the head, and knocks you overboard. Trust me. I know.