When making beer the hull is beneficial because if you use a hullless grain the mash becomes a big sloppy mass that doesn’t really drain well, like a super wet dough. The hull however breaks up this structure and makes the mash free draining meaning you can easily remove the liquids from the solids. Even beer like wheat beer is often still up to 50% barley because of this. Funnily enough the original mesopotamian beer was not strained at all. All the solids were still in there so it was chunky. They drank this beer with a straw.

Regarding how barley flour for bread was traditionally made. When you grind up whole barley the inner portion turns to flour while the hull tends to come out the other side pretty much intact because it’s quite tough. Therefore you can sift it through a sieve because while it is thin the hull takes up a lot of space in the other 2 dimensions. The house wives of old in barley dominant regions would do this near daily. While this works well it’s of course extra work compared to a hullless grain like wheat where the flour that goes out of the grain mill is ready to use straight from the get go. Of course nowadays we have industrial equipment that can dehull tonnes of barley per second.