Barrels is a perfect example of too many options to carry stock to satisfy the customers. Contours, twists, materials, length, caliber, shank diameter, etc.
Another pet peeve of mine is the amount of reticle patterns scope manufacturers produce. It is borderline ridiculous and makes it very hard on dealers to carry stock as inevitably they do not have the right one for somebody and they end up with thousands of dollars of inventory that are hard to move and end up special ordering goods with inventory on the shelf...