Esther, can't speak for anyone else but I would guess it has to do with the bond developed with fellow crew members due to enduring similiar hardships in addition to fond memories of the good liberty ports whether it be sights or brawls. After you have "done it" the next time you see a ship, cutter, boat or whatever, you instantly compare her, good or bad to your experience. Obviously, the flood gates are opened and the memories - 90% good ones - well up to the surface.
It has been 32 years since I was discharged. I associate the Coast Guard and my time on the Tam with good times, good friends, growing up, becoming a "salt" I was 19 then so it was not an "old" salt. I wouldn't exactly call a 205 foot behemoth of an ocean going tug a romantic notion of life at sea, but never the less I remember standing many a watch in a fog bound sea standing at the stem, listening to the water being sliced by the bow. I remember bone jarring assaults on my knees as I steered her through mountainous swells enroute to a search and rescue case. I remember forays into that evil
world of liberty ports arm in arm with 3 or 4 other coasties, pennies in our pockets still being able to have a good time and I remember the good feeling you had when you knew you made a difference. All of these things combine to make you stop and look twice at another boat and ruminate because of the memories they trigger.
At any rate that's my nonsensical explanation to your question.
Bill