It is because it was more than a silly slogan like 'Its not just a job, its an adventure'.
Submarines are a life, or to use a somewhat maligned term, a lifestyle.
On a submarine, you are in it, surrounded by it for days and weeks for us DBFers, and months for nukes. Inside a steel tube with men that you must live, work, laugh and every so often despite our best efforts, to die with. Your very survival depends on these men. You train them well, because it does mean so much to all aboard. Sure, you dont love them all, you cant... But you respect them because you know they are the best boat sailors. After all, they trained you and you trained them.
I think one of the things that ties sub sailors together, is that we are all connected by qualification. Not that we all did it, but that it really does connect us, all the way back to the Holland.
Recently, I have talked to two shipmates, one that I turned into a throttleman and one that qualed the man that trained me. Digging through our collective pasts there would be an unbroken line back to the Hollands 1 and 2-way trash dumpers and bilge wipers. I am proud to think that Im connected in a small way to men that took their lives in their hands every time they threw off #1 line. Men on boats that knew it was time to try to surface when the canary was belly up on the bottom of its cage from gasoline fumes.
We are their legacy, like the nukes of today are ours.