Celiac disease has been around for a long time, but I think that diagnosis is easier now than it was 50 years ago. And increased awareness along with the ease of the blood test probably make physicians more likely to order the test for patients with ongoing digestive issues. Food allergies have been increasing sharply over the past couple of decades, and the cause of this is only speculated, not known. I think there is also more awareness about food quality and the diet/health connection, that results in people avoiding foods that are everyday fare for some (I, for instance, would rather go hungry for a few hours than eat fast food).
My aunt was allergic to wheat, but I don't remember her avoiding it. Likely that she thought it too difficult in her wheat-centered family (immigrants from northern Europe). It contributed to her asthma and respiratory ailments - which ultimately caused her to die suddenly at the age of 39.