Because IBS is psychologically driven, excluding certain foods from the diet is not the solution. Since it is the
perception of certain foods rather than
physical action of certain foods causing the symptoms, psychotherapy would treat the ultimate cause.
Obviously, all these "gluten/wheat/FODMAPS are evil" messages drive IBS symptoms.
And the tide is turning against this thinking, with non-Coeliac gluten sensitivity being questioned as to whether this actually exists as a physical condition. Because people are increasingly being told and conditioned that they may get symptoms from certain foods, certain cohorts of people then expect they will get symptoms and start somatising them (or noticing things that they didn't used to)
As above.
What about people with egg allergies? Egg is in a lot of things.
Much of the problem of a person with Coeliac's Disease finding things to eat is that so much food for sale is so highly processed, with gluten containing ingredients finding their way into them. If somebody cooks from basic and raw ingredients, it isn't actually such an issue. Nobody needs to eat gluten containing products, so the state should not have to pay for people to eat gluten-free products.
The vast majority of people with real Coeliac's Disease (i.e not all these people with "gluten intolerance/sensitivity"
will avoid gluten irrespective of the cost, because the symptoms they get are so debilitating. This may not seem intuitive to the legions of "gluten intolerants" who 'feel a bit bloated' after eating bread (which is expected, bread is filling and supposed to make you feel full).