I don't know why they seem to do that, but there are patterns and there are numbers that tend to have significant purpose in the Scriptures as in being symbolic of the purpose for when they are used. But other than that I don't tie it to the numerology as is so easy to do, and I don't tie it to anything else other than what it actually stands for. My hunch is this, that the numbers are repeated so the ones who were involved at that time would be able to remember what happened when, and to tie it to the event itself and why it was to happen, is because God wanted it to happen that way and not for any other reason.