Why would surgeons refuse to undo a repaired colon left with a pouch outside of the body?

several reasons: When peritonitis develops due to reputed diverticulitis , left colon rectosimoid colon resection , end will become pouch ( colostmy ) later will be reattached hartman's procedure , also done in cancer, it is not reversed for several reasons , if medically unstable, non compliant pts, unable to loose weight, or had , end stage cancer with limited life expectancy , your could be any one of them