I have really bad carpal tunnel.... with straight neeldes i can only knit for a short amount of time before my wrists hurt so bad i have to pull out the aleve and alternate heat and ice. With the circulars, i can knit for hours on end (no kidding, i knitted through our lord of the rings movie marathon) and have no problem with my wrists.
All of the above reasons, plus the "oohh factor". "Oohh, what are you doing with that yarn?" It's magnified when you're using the magic loop method in public. I knit at our public library while reading magazines sometimes, just 'cause my hands get bored.
I LOVE THIS SITE!
"All good things and every perfect gift is from above, coming down from the Father of Lights who cannot change."