I agree with Eric. I see no bashing on his part of the English frame. Perhaps a general comment about design choices and Eric's preference for such. If people don't thing that bike frames (and components) aren't made with a lifespan in mind then you're kidding yourselves.
Back to the OP's question- There are many reasons to not make integrated racks on a loaded touring bike. Why make and charge custom fab fees for something that others make real well and for less? Why dedicate the load bearing parts that have a history of failure and therefore make tour side repairs much more involved? Why limit your rider's choices to only the current design or the current intended use?
I don't have any third world touring experience but have done self contained tours for over 40 years and for 35 years on my own frames. I would never use an integrated rack for a loaded tour. I have made a few such racks over the years. From simple designed ones (using K&S brass tubing) to hold my spare sew up to this one on my errand bike. But I value the ability to repair or get a
round problems while touring. All the possible repair methods that apply to a integrated rack also apply to a Tubus steel rack. Except for the ability to replace the rack with one that's available locally. Andy.