Now that's staying power. There aren't too many sunken vessels that retain their charisma throughout a century. Consider the RMS Lusitania, which was sunk by a German torpedo in 1915 and lost nearly 1,200 passengers. It doesn't have a half-dozen Hollywood movies about it, plus a best-selling, Oscar-winning theme song.
I doubt many high schoolers today would know about the Lusitania. In fact, a fair amount of adults probably couldn't identify it. What is it that makes the Titanic such a powerful story?
It may be the arrogance of the now-famous assumption that Titanic was unsinkable, as reflected in the various quotations linked here, that keeps the ill-fated ship so famous. Warnings of icebergs in the ship's sea lane were ignored and her speed was increased, despite the fact that Titanic held lifeboats to accommodate only half of the passengers. Titanic Capt. Edward Smith learned the hard way that it's not a good idea to put too much stock in the superiority of modern technology.
Or, perhaps Titanic's enduring appeal is due to the unfortunate string of sad coincidences that thwarted a rescue--the distress rockets that went unacknowledged, the captain and radio operator on the neighboring ship SS Californian who had retired for the night minutes before the disaster, the lifeboats that pushed off only half full of survivors.
Possibly most riveting are the personal stories of valor, cowardice, and survival that lived on after the ship. I think this human, almost personal element of the best and worse behaviors our species has to offer is the reason that Titanic holds such a grip on our imaginations. As long as there are brave people who are willing to give up their own lives to save others, or despicable ones who will stop at nothing to preserve their own skins, it's likely that the unforgettable story of the Titanic will go on...and on.