The Mayan calendar is very complex because it was important to them to know and understand a tremendous number of cyclic events. Their calendar 'starts' and 'ends' at a confluence of all those cycles.
My cut at it is they figured why do "page" 2 if "page" 1 is exactly the same.
If it mattered to us enough, we would have a seven year calendar... where the date and day matched. Or a lunar calendar that was 33-34 years long, matchng a date to a particular phase of the moon, or a 210+/- year calendar matching date-day-and lunar phases... But those things don't matter to us, so we have a one year calendar.
Here's a great wikipedia explanation.
BTW, the source of the end of the world theory is a New Age concept... If someone were to offer it today for the first time and you'd label it cultist. From the wikipedia article: "The Mesoamerican Long Count calendar forms the basis for a New Age belief, first forecast by José Argüelles, that a cataclysm will take place on or about 21 December 2012."
All that aside...