Fire danger and the "leave no trace" idea. We have been doing this for years while on multi-day river trips. We don't have to worry about fire danger in a lot of camps along the rivers. However, everyone using a fire pan and carrying out the coals/ashes allows everyone to have a more pristine experience, or at least a cleaner camp when they arrive for their use. It's really not that much work once you get into the routine.
Totally agree. Fire danger is extremely high in Big Bend, I'd hate to be responsible for a giant brush fire, not many resources to fight it out there.