Good question. But if they let people with celiac into the service, then they do need to offer them something their digestion can handle.
In my case, if I ingest even a molecule of wheat flour, I will be sick for 14 days. The symptoms are that your own intestinal antibodies go to work, attacking not the gluten, but the intestine, producing incessant lower GI rumbling and turmoil. It can be very debilitating.
For people with celiac's, gluten-free is not a fad diet.
And it has been getting easier to cope in the past couple of years. Tried Bob's Red Mill All Purpose flour? That stuff is great! I use it just like regular flour. It won't make bread like regular does but for almost everything else it's terrific.
Eating out isn’t really worth it. Not very many restaurants can manage the cross contamination and a lot don’t really care. I guess it’s a pain for them and too many people are “GF” in name only.