The seed coat is really a fruit coat. Barley is used primarily in beer making.
Brewers use barley as a source of sugar to make the alcohol for beer.
Brewers knew that sprouting the barley seeds improves the sugar yields tremendously, but they wanted even more sugar yield. The brewers came to plant physiologists to find out if anything could be done. The sugar content of a dry barley seed is actually quite low, but the endosperm holds a huge reserve of starch. Starch is a polymer of sugars. In a sense it is a long chain of sugar molecules linked together.