I love IEMs and have been using them for years but theres times where I feel uneasy with them, especially when commuting. I always worry about the rubber tips popping off (which they have before and it sucks cause no tip = no use for the headphones til i get home to put a new one on). Now only that but the tips can be a pain in the ass ordering new ones from time to time. I also feel uneasy about putting them in my pocket in fear of squishing the cable or dust or lint getting inside them. Im always cleaning them.
Cans, even though not as portable, you can just wear around your neck instead of cramming them in a pocket. They also stand out more. From what i was told, girls dig guys with big headphones. Also they go on instant, whereas IEMs you have to hold for few secs for the isolation and often have to take out and reinsert for a new fresh seal. Only bad thing about the cans is that they squish your ears! And can be bit uncomfortable for anyone wearing glasses. And it ruins your hair!