There's more to the story. You can get an endoscopy & biopsy to get tested for Celiac's, but mine came back negative. My doctor said they can only detect about half of gluten intolerances using current medical tools like IgE blood tests & so on; we don't have the technology to identify the remaining cases yet. I'm sure some people use gluten intolerance as a fad diet or for weight loss or even for attention, but it's also a legitimate issue for a lot of people. Personally, I have no idea why you would give up gluten (sandwiches, pizza, croissants, dinner rolls, breakfast cereals, hotdog & hamburger buns, fried chicken, cookies, cakes, etc.) willingly. It's extremely hard to cut out of your diet because they put it in nearly everything these days; if gluten really makes you feel ill, it's a total nightmare because you have to completely change how you eat, how you shop, going out to eat with family & friends, everything. Can also add a lot of expense to your food budget if you like to bake or cook & want to make similar meals without the wheat. A small bag of almond flour is like twelve bucks!
The second problem is that there is more than one source vector for the root cause. There is growing researching linking glyphosate (Roundup) to gluten intolerance. For me, it turned out to be SIBO, which was caused by a surgery I had as a kid. Eating gluten caused a range of non-deathly symptoms (i.e. I never had to use an Epipen because it didn't constrict my throat) such as anxiety, coldness, arthritis, brain fog, fatigue, etc. because I wasn't able to digest it, and it was too far down the GI tract for the endoscopy to see, so it went undetected my whole life until I learned about it this summer, got the special test done (3-hour breath test), and got treated for it. Being able to eat gluten again is amazing. But even after half a lifetime of research, I had never even heard of this condition until a few months ago. There's just so many things that can go wrong with your body, and they're discovering new things all the time. For example, SIBO only really got traction a few years ago & most doctors aren't familiar with it at all yet.
Unfortunately SIBO is not the root cause for everyone, and we just don't have the medical tech to diagnose every root cause yet, so we're stuck with people with the flat-earth mentality who feel they are experts chiming in, adamantly, to say it's not real, which is frustrating because then you not only have to deal with feeling crummy all the time, but also with people telling you it's all in your head. It's like saying cancer isn't curable...we don't have the technology yet, but that doesn't mean it won't ever exist, and progress is being made. Look at the history of medicine...we struggled for years with tetanus, rabies, polio, yellow fever, measles, smallpox, and all of those are cured now through medicine & vaccinations. Right now, a ton of people are complaining about feeling mildly sick all the time from eating wheat-based products & we don't have a definitive answer...yet. Especially if one of the root cause does turn out to be something like glyphosate, that's more than likely something that has to be tracked long-term like smoking cigarettes, which people were in denial about for decades until the medical science came out & proved what was happening.
TL;DR - you can get tested, but that is only valid in half the cases. My gluten-related issues did not show up on any allergy test. Ate it, felt like crap, cut it out, felt better. It ultimately ended up being a different root cause which required a specialty test, which fortunately was managable (not curable) & I can now eat gluten without consequence.