medicine is a scientific discipline. In order to have a "disease" you need to have a deviation or interruption of the normal function or structure of the body that has characteristic symptoms and signs.
In other words measurable data to show the "malfunction" needs to be present. Also the malfunction has to be related to the findings of the causative agent.
Chronic fatigue may in fact exist. But the causative agents that can be replicated in blinded studies don't exist. Anecdotal evidence is one thing but the science has to back it up.
An example is if you have a patient that drinks water and beer, whiskey and water, tequila and water, scotch and water and all patients get drunk... it must be the water causing it. Unless you do the studies to have patients drink water alone and with other compounds you'll never understand that the alcohol in the fluids causes the drunkenness.
A lot of feel good, politically correct stuff is creeping into medicine, so don't worry. Chronic Fatigue will get to be a disease that qualifies for SSI disability just like ADHD, alcoholism, heroin addiction and chronic back pain.
Unfortunately, until a traditional disease entity is officially established and can be tested for in the clinical setting, patient complaints and symptoms suggestive of CFS are mostly disparaged and ignored. This is so even when closer attention to the nature of those complaints and more diagnostic effort could result in relief for the patient — and from well-recognized diseases at that.
Currently, diagnostic skills are taught and applied in a formulaic fashion. Just as the kitchen help in a McDonalds cannot depart from the menu items, too many doctors are a loss when patients do not present symptoms that fit accustomed diagnostic patterns. Atypical cases and protean disorders are often missed.
Today, CFS is just an easy way to put a troublesome category of patients into a category of permanent illness that calls for little further effort at diagnosis and treatment. Objectively though, celiac disease and atypical shingles are a good fit for many cases of CFS. I know of no medical authority though that even suggests that they be considered and excluded when CFS is suspected.