This means you have an hermetically sealed unit which rewinds itself as you live your life, and works off its reserve when you put it aside. This unit runs off mechanical energy, with no electricity whatsoever, and keeps time pretty spot on for what it is.
Moreover this steel+sapphire construction is made to held up against daily elements and some (a 30 bar designation is no slouch), over the decades you presumably own the piece.
As a result, you carry something you can depend (and love to look at) for a very long time, and live your life together, in a sense. Long living items collect memories with you, and act as a trigger for these memories too.
This is very different from an item which you consume and (have to) throw away three years later. This is why some people are this much into watches, fountain pens, and other low tech items which have long lifespans, presumably generations.