Because as Mrsowen explained the company needs to make money to stay competitive and continue to thrive so they need to sell things other than just b/k. There aren't enough bags for everyone so they prioritize selling to people who enjoy the brand as well as the artistry and craftsmanship. It's not a value judgment. It's business.
Completely agree with what Pocketbook says. It is good for their business with customers that keep coming back to buy different types of items. I am sure this is particularly true for stores who are less frequented by tourists and why those stores might appreciate (or require) some purchase history before selling their most sought of bags.