Short and sweet, I saw this quote from Dr Peter Osborne today and thought it was a brief, but useful summary of how to explain true gluten sensitivity and why its important to know if you have it:
Gluten Sensitivity is not a disease, it is a state of genetics.
When gluten sensitivity goes unidentified it triggers disease (on average at about the age of 45). Many of the diseases triggered by gluten are autoimmune in nature. Autoimmune disease typically take years to manifest and diagnose (this is why the average person is diagnosed so late in life). Celiac disease is just one of the many manifestations of disease induced by gluten.
This is quite a useful explanation of why you need to give up gluten grains if your test results show the genetic pattern for gluten sensitivity.