Can someone please explain this whole hanging a tin mug off your bag shit? To me, it just looks like you cannot pack your bag properly! Get a Ti mug and then at least you can put it on the stove top.
Easy. Because it looks cool! Tells other folk you're going on a ride and have the wherewithal to make a hot tasty beverage in the great outdoors. Or it just means you're a bike riding, flannel wearing, beard stroking hipster! But I could be wrong.