Starbucks is a terrible example. That's like claiming the Costco membership makes the Costco retail business the auxillary. Or that Kroger/CVS/Walgreens membership/rewards cards do the same for those retail businesses (when in fact all they do is drive higher rates of return visits and higher sales).
The Starbucks business remains almost entirely their retail service business.
The Starbucks business remains almost entirely their retail service business.