Companies like Kohler, Delta and Moen also make exclusive lines for HD & Lowes. Most of the time, it's cheaper parts to keep costs low. The biggest thing big box stores do is attempt to carry the brands the other store doesn't carry. If they can't get brand exclusivity, they sell the tools and models the other store doesn't stock. Even if it's the EXACT same product, they get the model number changed by one character. Minimizes price wars and price matching. It's the best they can do to manipulate free market and competition which keeps prices low. They leave it up to the manufacturers to deal with competition and pricing. Many products aren't even "re-sold" by Lowes and HD. Some are literally on consignment. Many big ticket items are sold at or near cost to HD, and in return, compensated for prime shelf space.