I put on a type Type 3 life vest non-inflatable with pockets, when I leave the car to walk to the boat and take it off before getting back in the car.
There have been many cases of drowning at the dock.
Most people think they can determine when the conditions are such that they "need" a vest. Every month during the summer there are at least two guys that drown without a vest right here in long island sound. It seems that most of them have years if not decades more experience than me. Apparently they guessed poorly.
In my opinion you "need" a vest if you are on anyplace where a simple misstep can put you in the water. That includes dock or boat. The exception is swimming at anchor when someone is assigned to life-guard duty.
A couple of years ago at about 6 AM I was walking from the bedroom down the hall about 20 feet to bathroom in my home. About half way there I slumped against the wall and was very dizzy. Did not fall but had a hard time controlling my limbs to make it to the bathroom. On the way back I was fine. I spent about 5 days in the hospital, they ran every check on me possible and could find nothing. If that would have happened on a boat or dock I very likely would have been overboard.
All it takes is the smallest misstep.
A line breaking.
A boat wake
A moment of inattention
A winch spinning out
If you are lucky someone sees you immediately. If not you swim for, what 30 minutes. You can't even get into the survival position to conserve heat if you don't have on a jacket.
Depending on the water temperature the difference between with and without a jacket can be hours when even minutes can be enough to save your life.
I'm more than happy to be the nerd who wears the jacket at all times while the cools guys wear the racing t-shirts. If it's good enough for the coat guard it's good enough for me.