Perhaps that is the case when one looks at a large group. But my hubby used to be a grave digger and the deaths really did come in threes. It wasn't three graves in a row and then start immediately over. It was in threes and then a break before the next batch. Strange.
It's how people count. If they always go in threes then what were the other 2 when Andreas Katsulas died two weeks ago? People who think things happen in 3s always notice clusters that match their pre-conception, or manufacture them by forming clusters, and ignore the ones that go against.