I still remember the group of men on an Air Force aircraft that decided to use the heaters to cook their MRE's while the plane was in flight:
Unfortunately, those 30 heaters produced enough gas to set off the planes explosive atmosphere indicator in the back...and the pilot, not knowing what was wrong with his plane, set it down for an emergency landing.
Not real funny.
I also remember the guys that was doing the MRE heater thing in the aluminum 3 By wall shelter...the two heaters had their gas set on fire by one of the guys cigarettes..kinda interesting to see them putting that mess out.
well LCDR_SurfWar is right; the bags take up less space, are lighter, are not as labor intesive to make, are designed to be a "flutter drop package" as proved in afganistan, and allow the user free plastic containes the are rough, tough, and can be made into many useful things.
Plus, when broken down further, the inner packages fit easily into the Pockets of the BDUs