Culture is made of shared experiences. Television, movies and music make many of those experiences repeatable, so that people can be part of a culture without having to be at the same events at the same time. When you think about it, that's kind of weird. The basis on which I relate to you is, to a large extent, the movies, music and television we have both seen, whether or not that was together. And when we find something that one of us has seen but the other has not, you can go away and fix that, rather than being left out.
Mokalus of Borg
PS - This is only as we get to know each other, though.
PPS - After that, presumably we do have some significant shared experiences of our own.