Imagine having Crohn's disease the year before it (or UC) was 'discovered.' You had a debilitating disease, but you were just told you had "really bad irritable bowel syndrome". Certain doctors would tell you that it was all in your head. Or at the least, they would be wholly unhelpful. The general public would be much worse.
In my extensive experience, doctors are really, very much just people. Actually, they're often less helpful than regular people because they have extreme constraints on their time and against thinking for themselves (example of the latter: a close friend of mine was hospitalized for attempting suicide and they wouldn't give him benzodiazepines because of the __risk of addiction__).
Sorry for the rant...
Individual doctors do better or worse at dealing with patients who fall off the map of known problems and solutions - from accusing patients of lying about symptoms to referring them to medical researchers to just explaining that there's not much they can do but keep an eye on the situation - but the most important thing, medically, is for the doctor to make sure that your symptoms don't have a known, treatable cause.
Dying or suffering for years from a mysterious condition sucks; dying or suffering for years from a well-known condition that just went undiagnosed sucks worse.
In UC/Crohn's, patients presented with recurrent bouts of bloody diarrhea in the absence of infectious symptoms, with possible associations of malabsorption, fistulas, and colon cancer. These are pretty straightforward things to diagnose and clearly represent pathology, irrespective of whether we can assign a name to them.
CFS includes symptoms that don't fall so far from the range of 'normal' human experiences, thus it's much harder to define syndromically.
IBS is an interesting choice for comparison, as it, like CFS, seems to be in part a psychiatric diagnosis at least as it relates to stress. Nothwithstanding, there are clear associations for IBS - chronic abnormal bowel movements and abdominal pain, neither of which is 'normal'.