Wheat is also another one that commonly causes issues for people with compromised digestive systems.
I have some thoughts on why gluten intolerance/sensitivity and celiac seems to be increasing quite a lot in modern times.
It may be a confluence of different factors such as: Modern forms of wheat are much higher in gluten than more ancient and less hybridized forms.
Up until the the earlier 1900's, most bread was sour dough made. Sour doughing bread and wheat, is somewhat akin to turning cow milk into yogurt or the like. With sour dough cultures, you have a wide mix of bacteria, yeast and sometimes other microbes that help to break down and predigest the wheat, ultimately, making it easier for you to digest. Similar to cow milk and yogurt. Now, most wheat breads are made with a single strain of yeast. This has become the most commonly consumed forms of bread in many countries.
Modern forms of super yeast are more specialized and do not pre digest the various substances in wheat like a sour dough culture does. The yeast concentrates on the starchy/sugary part for it's food source and not so much the proteins (which gluten is).
The increasingly popular and exported "western" type diet has become rather unhealthy in many respects, which in itself compromises people's digestive systems.
Add those 3 factors together, and it makes a lot of sense why gluten intolerance/sensitivity and celiac disease is on the rise. People's bodies are quite frankly rejecting that which it can not fully and properly digest. The exception to this, is course cellulose/fiber, which we've been eating since we've been around and which provides a very necessary cleansing function for us which is why our bodies don't reject it like partially undigested proteins. Proteins also resemble more the various pathogens that cause problems for us.
Anyways, speaking as someone with a compromised digestive system, i feel better when i avoid wheat and gluten. My body seems less sensitive though, to things like well sour doughed spelt bread for an example. However, for a true celiac it will still cause problems because any trace of unbroken down gluten elicits severe reactions. A more true "allergy" has built up in such a case.
Note: i'm not medically trained, but have been researching, studying, and experimenting with diet and holistic health since age 16 out of necessity due to some unusual and at one time, very uncomfortable body imbalances.