I am not going to detach and attach a cable every 5 minutes when I come to an exercise that I feel like has the cord get in the way. Music keeps me amped during my lift, and when you are at the gym for an hour or so, I just find it personally troublesome to detach the cord on and off between exercises, let alone if I choose to do it through sets. Also, on some exercises like Deadlifts and Preacher curls, the cord is pressed (it leaves a mark on what part of skin the cord is pressing) or gets in the way. I either take the headphones/cord off, or I can have the luxury of having a wireless pair, so I don't deal with any cord worries.
Plus, when I'm shooting hoops for an hour and practicing, I'd rather have music in my ears than no music at all. Once again. Having a cord outside my shirt gets in the way at all times. Lord knows how many times my headphones have been yanked while shooting. I'm not a fan of having it under my shirt as previously stated.
Also, you guys missed the part where I said in general, I'm just always on the move, so I don't want to deal with a cord when I'm outside my house. For example. When I was leaving class one time, my headphone cord got caught on a part of the desk and the wire snapped. Another example is being at the library only to have my cord get snagged by something along the way.