Achilles and His Heel

Do you guys remember the story about the legendary Greek hero, Achilles?  If not, do you at least remember the 2004 movie Troy which starred Brad Pitt as the legendary Greek hero, Achilles?  Yeah, I know that that movie isn't a great example of cinematic history, but it covered the gist of Achilles's story.  In any case, the Greek mythology behind Achilles is that he was the son of the nymph (some sort of fair, I think)  Thetis and the King of the Myrmidons.  When he was born, his nymph mother wanted to make him immortal and she achieved this by dipping him in the river Styx.  However, because she held him by the heel, that part of his body did not absorb the magic of the river Styx and was very much vulnerable.  With that out of the way, I have a couple of very big questions about his death.

If you don't remember, the legend is that during the Trojan War, Achilles helped Agememnon besiege the city of Troy because the Prince of Troy, Paris, stole Agamemnon's brother's wife, Helen, when in reality he was just looking for a reason to attack Troy all along.  While Troy was being sacked (and after those idiots didn't bother to check to see if anyone was hiding inside a giant wooden horse), Paris shot and killed Achilles with an arrow that hit him in the heel.  So, my first question is - how exactly does someone die from a simple arrow to a part of the body that holds no vital organs or large arteries and is in fact, just a large shock-absorbing muscle?  I could understand if Achilles's mom dipped him into the river Styx by holding his temples and he was shot by an arrow there, but no, he was shot in the heel.  The aftermath of an arrow to the heel would be that he couldn't walk on it for awhile, but certainly not death.  The only way that he could have died from this injury is if that arrow was poisoned or some meddling Greek Gods got involved.  Sure enough, that is what they claim happened in a couple of versions of the story, but not in the most famous story about Achilles, Homer's Iliad.

My next question is - if Achilles's mother knew he was vulnerable in his heel, why didn't she tell him?  And if she did tell him, why didn't he just where a piece of armor that protected THE ONE SPOT on his body that could get him killed?  Here's an idea Achilles, wear high-top sandals or a piece of metal that wraps around your ankles.  In fact, wear nothing but a piece of metal around your ankles, it's not like a blow to the head is going to do any harm your invincible body.  The Greeks told a lot of crazy stories, but this one takes the cake in stupidity when it comes to an easily avoidable death to your greatest hero.

"If he was invulnerable, then why in the hell is he wearing armor?  Why wouldn't he just fight naked?  That would certainly give him the element of surprise."