You're right - they aren't treating their condition, they are trying to discover how not to aggravate whatever it is that's wrong with their system. And this really is something which doctors should know about and be able to prescribe: "Here, try this diet and tell me if you have any symptoms." before giving them experimental drugs with nasty side-effects. It won't help us understand how the condition works, why it happens and indeed, won't cure a person, but it will let them live like most everybody else at a minimal cost.