Why would you possibly want to knit a sweater when you can just as easily (actually, WAY more easily) pick one out from a store? That's the question my brother asked me over winter break, when he found me curled up in a chair with an armful of yarn and knitting needles. (For the record, he also called me an old lady and laughed at me.)
Luckily, I had plenty of answers to his question. Case in point: if all you do on your daily commute is cruise Facebook only to be tortured by status updates of your friends' vacation photos, you should try knitting. If you need a distraction from the croupy toddler coughing next to you in the doctor's waiting room, you should try knitting. If you've ever wanted to give the illusion of being "busy" to avoid awkward family discussions, or if you've ever felt the need to accomplish something tangible with your own two hands, you should try knitting.