The question here is: why are we so interested in anniversaries? And although no direct answer is given to it, this is offered as one of the effects of that interest:
[A]nniversaries are to be praised because they constitute a historical review system allowing us to think about just a few things at any given time rather than trying to think about everything all of the time.
Review system, maybe; but allowing us to think about just a few things at a time I don't buy. We're both allowed and able to be selective anyway, without the aid of anniversaries. You don't celebrate your child's birthday so as not to have to think about your other children. So why? It's just the interest we have in connections, isn't it? Connections whether causal or accidental, meaningful or arbitrary. That's why some people will note that this score, made by Australia (or whoever) on this ground today, is identical to that score made by them on that ground 11 years ago; or that Darryl shares a middle name with Brendan; or that Sheila shares a birthday with Maria; or that Charles Dickens once lived in that house. It's a way of organizing what would otherwise be chaotic.