Why so surprising?

When I knit in public, I get odd looks, double takes, and people exclaiming that they didn't know you could knit with three needles. Why are they so surprised? What is so extraordinary about a girl my age knitting on DPN's?
The comments and looks I get are funny but never hurtful. No one has ever said to me; "Isn't that the sort of thing that old ladies do?" No one has ever called me granny, no one has scoffed at my lifestyle.
One such comment was particularly funny. Sitting in a lodge at a camp weekend retreat, a middle school boy across from me exclaimed "Woah! I didn't know you could knit like that!" he was fascinated with my craft. Maybe I should steal Kelley Petkun's idea and make a sign that says "Free Knitting Lessons".
But the boy watched in fascination none the less. He had apparently seen my shirt earlier. I was wearing my Metal Head Knitter t-shirt. He said, "Unzip your sweater and show them your shirt! It's so cool!" I showed them the shirt, it has a Metal Head skull and crossed needles.
The point of my rant is, why are people so surprised? Our craft is thousands of years old, people used to do it just to survive. So, in the 21'st century, with our mass produced socks, scarves, and sweaters, knitting is for the elite, the few and far between who have the courage to shake our needles at the factories and cheap sock producing sweat-houses of the world. The question is, are you ready to knit in public and take on the fight? What is our fight? We are fighting the images that knitting is done by little old ladies in rocking chairs with a shawl over her shoulders. Not that there is anything wrong with that, but there is more than one image of a knitter. Including a teenaged girl in an airline seat with her iPod.