Dermatologists still prescribe antibiotics for acne. For some specializations, it's all about the maintaining the status quo.

Truth be told, doctors still don't know much about IBS and/or Crohn's. Or even conditions like rosacea and/or dermatitis. Mark my words, better gut flora/microbiome will be the cure for these conditions in the near future and doctors will contest this up until the evidence is too loud to ignore.