I don't exist because other people exist
Maybe "existence" was an exaggerated term. Maybe it would make more sense if I had said: "existence is the capacity of making yourself worth of something", but then I would not be referring to existence at all.
I do not exist for those who will never know of my existence. If nobody knows of my existance, do I exist?, or do I matter? Life is all around me, but it doesn't acknowledge my existence, because it does not need to. Do I exist if I'm the only one who knows of my existence?
(maybe I recognize it doesn't make any sense)