Tbf, most grains have way more gluten in them than they used to, though wheat is by far the worst offender. This is because they’ve been bred for industrial purposes. If you have a grain with a lot of gluten it’ll rise more, so you can use less wheat (aka reduce cost) while keeping the size of the loaf the same
There most certainly is gluten in barley! Breweries don’t just add gluten to beer just to be dicks to people with celiac disease.
Tbf, most grains have way more gluten in them than they used to, though wheat is by far the worst offender. This is because they’ve been bred for industrial purposes. If you have a grain with a lot of gluten it’ll rise more, so you can use less wheat (aka reduce cost) while keeping the size of the loaf the same