I'm not in "business" like many of you but I'm of the thinking when I cook bbq for people who come to my house I want to serve them something they can't get anywhere else except from me. And I would think if I were in business for myself I'd have that same mindset.
Uniqueness in what you offer is a major part of the component of return business. And the more "uniqueness" (diclaimer: GOOD UNIQUENESS) you have in your business then the more return business you're likely to have. Is there anything *wrong* with using a commercially sold sauce that comes from Wal-Mart? Nope. But it will not contribute to the component of return business. Because as someone has said above. People, with regards to the sauce, will potentially say "This sauce taste just like ______ I get at Wal-Mart." And and you really don't want that response to many elements of your business.