I believe the only reason this subject is even being discussed is that:
(1) It is a concrete date.
No other civilization lost to the sands of time has given so unambiguous a date for any event, no matter how mundane.
(2) The date in question is "at our doorstep", so to speak.
Whether we take any stock in it or not, it is something happening in our very lifetime, so it enters into our culture and our collective conversation whether we like it our not simply by virtue of the fact that it is NOW.
Personally, I like the Bible's proclamation that "no man will know the day or the hour", so basically setting a date is kinda pointless.
P.S. Here's an easy read on Mayan math and date reckoning:
As far as I tell from that and Wikipedia, the calendar does not
end in 2012. At best, that is (possibly) the end of one cycle. The Meso-Americans seem to have counted days rather than years (presumably because seasonality was not so marked as in more northerly latitudes). As with Julian Day Numbers, it's easy to count back without having to worry about leap years and the like. They counted in base 20, but the Long Count seems to be based on notional years of 360 days (the same as the Babylonians used). To help them keep track, they had twenty day names, which they numbered modulo 13, so that after 260 days the pattern of day numbers and names would recur. The start of the Long Count has been calculated as August 13, 3114 BCE, though I doubt if the actual counting began so long ago.
So what cycle will end in 2012? 13 x 20 x 20 360-day years. If you are counting of 20-year periods (the third digit space on a Long Count date), one cycle of 260. Is that significant? It's a bit like saying "a year of generations," or the various schemes based on "a thousand years as a single day."
If pre-Mayan peoples did think in terms of cycle of this length, then perhaps the Long Count began ca. 550 BCE., when whoever started it supposed themselves at the midpoint. I wonder what they would have thought if they could see the result?